Math and counting

Number theory, combinatorics, and geometry

Under construction

Still being built. Things may change

Total results13,153 problems

Vote Counting
Easy2
Implementation, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
The Train at the End of the World
Easy2
Implementation, Geometry
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Artistic Souvenir
Easy2
Math, Geometry
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Drum
Easy2
Implementation, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Haru Dermatology
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
What Makes 2023 Special?
Easy2
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Dice
Easy2
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Clever Ines
Easy2
Implementation, String+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Clock
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Time
Easy2
Implementation, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Triangles
Easy2
Brute force, Geometry
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Rectangle
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
I Thought of a Number
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Fakir
Easy2
Implementation, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Cutting Colored Paper
Easy2
Math, Implementation
No attempts yet
Time limit
0.5s
Memory limit
1024 MB
Judgeable
Rampant Growth
Easy2
Math, Combinatorics
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Clock Tower
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Special Technology
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Watermelon Game
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Malatang Tanghulu
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Placing Game Pieces
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
PE Is a Math Subject
Easy2
Math, Implementation
No attempts yet
Time limit
0.5s
Memory limit
1024 MB
Judgeable
I Want to Go to DIMIGO!
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Sejong's Time Travel
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Rhythm Game
Easy2
Implementation, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Dartboard
Easy2
Array, Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Fractions are better when continued
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Expected Error
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Composed Rhythms
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Building Pyramids
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Expected Eyes
Easy2
Math
No attempts yet
Time limit
4s
Memory limit
1024 MB
Judgeable
What Is a Human
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Which Number Kind Is It?
Easy2
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
Gahee and the Electricity Bill 1
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Generalized FizzBuzz
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
The Coin God Geonmo
Easy2
Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Consolidating Windows
Easy2
Math
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Chips
Easy2
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Graphs and Graphs
Easy2
Brute force, Implementation+1
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Bitcoin Halving
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Jjin Even Number
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
1024 MB
Judgeable
Either, but Not Both
Easy2
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Hezardastan's Annual Report
Easy2
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Divar's Salaries
Easy2
Implementation, Math
No attempts yet
Time limit
1s
Memory limit
2048 MB
Judgeable
Defense Clock
Easy2
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
1024 MB
Judgeable
I Flipped The Calendar...
Easy2
Implementation, Math
No attempts yet
Time limit
2s
Memory limit
2048 MB
Judgeable
Sum of a Sequence
Easy3
Math, Brute force+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Divisors
Easy3
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Guitar Strings
Easy3
Brute force, Greedy+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Tournament Meeting Round
Easy3
Simulation, Math+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Addition Cycle
Easy3
Simulation, Math
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Underprime
Easy3
Number theory, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Least Common Multiple of at Least Three Numbers
Easy3
Math, Brute force+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Strange Multiplication
Easy3
Math, String+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Dice Sum
Easy3
Brute force, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Binary Addition
Easy3
String, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Alphabet Diamond
Easy3
Simulation, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Lee-myeon and Im-hyeon
Easy3
Number theory, Implementation+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
D-Day
Easy3
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Decimal Digit
Easy3
Simulation, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Missed Call
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Arithmetic Progression
Easy3
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Hockey
Easy3
Geometry, Implementation
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Lottery
Easy3
Combinatorics, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Binary to Octal Conversion
Easy3
Bit manipulation, Math+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Eumha Railway 998
Easy3
Geometry, Math
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
K-Sejun Numbers
Easy3
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Walking
Easy3
Math, Greedy
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Make It One
Easy3
Dynamic programming, Math
No attempts yet
Time limit
0.15s
Memory limit
128 MB
Judgeable
Date Cycle Calculation
Easy3
Simulation, Math+1
No attempts yet
Time limit
2s
Memory limit
4 MB
Judgeable
Diet
Easy3
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Guitar Concert
Easy3
Bit manipulation, Brute force+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Maximum Product
Easy3
Math, Greedy
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Largest Lucky Number
Easy3
Recursion, Brute force+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Count Numbers Made Only of 4 and 7
Easy3
Brute force, Combinatorics+2
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Lost Parentheses
Easy3
Greedy, String+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Yongsik Goes to Camp
Easy3
Simulation, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Youngsik and Friends' Ball Toss
Easy3
Simulation, Implementation+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Modular Exponentiation
Easy3
Math, Number theory+1
No attempts yet
Time limit
0.5s
Memory limit
128 MB
Judgeable
Seongjun and Chocolate
Easy3
Simulation, Brute force+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Number of Trailing Zeros in a Factorial
Easy3
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Prime Palindrome
Easy3
Math, Brute force+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Multiple of Three
Easy3
String, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Firework Show
Easy3
Array, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Extended Fibonacci Numbers
Easy3
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Sum of Distinct Numbers
Easy3
Math, Binary search+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Logic Professor
Easy3
Brute force, Math
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Encryption Key
Easy3
Number theory, Math+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Safe Password Check
Easy3
Number theory, Math+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Broken Odometer
Easy3
Math, Implementation+1
No attempts yet
Time limit
0.5s
Memory limit
128 MB
Judgeable
01 Tiles
Easy3
Dynamic programming, Math
No attempts yet
Time limit
0.75s
Memory limit
256 MB
Judgeable
Tower of Hanoi
Easy3
Recursion, Math+1
No attempts yet
Time limit
6s
Memory limit
128 MB
Judgeable
Triangle
Easy3
Geometry, Implementation+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Find Prime Numbers
Easy3
Math, Number theory+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Counting Consecutive Sums
Easy3
Math, Number theory
No attempts yet
Time limit
2s
Memory limit
32 MB
Judgeable
Rounding
Easy3
Math, Implementation+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Completing a Magic Square
Easy3
Math, Matrix+1
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Negative Binary
Easy3
Math, Implementation
No attempts yet
Time limit
2s
Memory limit
128 MB
Judgeable
Pebbles
Easy3
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Statistics
Easy3
Array, Sorting+1
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
Vote CountingGiven vote counts for several candidates, print each count as tally marks with groups of five drawn as ++++ followed by a space.	Easy2	ImplementationMath	No attempts yet	1s	1024 MB	Judgeable
The Train at the End of the WorldGiven N stations joined in a chain by straight tracks, print the coordinates of the lowest point (smallest y) on the railway.	Easy2	ImplementationGeometry	No attempts yet	1s	1024 MB	Judgeable
Artistic SouvenirGiven the area of a circle, find the smallest square area that holds the circle with at least a 1 cm margin on every side.	Easy2	MathGeometry	No attempts yet	1s	1024 MB	Judgeable
DrumGiven hit counts X (left hand) and Y (right hand) per beat, print the order of hits in one beat: 1 for left, 2 for right, 3 for both.	Easy2	ImplementationMath	No attempts yet	1s	1024 MB	Judgeable
Haru DermatologyGiven a quadratic f(x) and a line g(x), compute the integral of f(x) minus g(x) from x1 to x2, which is an integer.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
What Makes 2023 Special?Given a four-digit year N that is not a multiple of 100, check whether N+1 is divisible by the last two digits of N.	Easy2	MathImplementation	No attempts yet	2s	1024 MB	Judgeable
DiceGiven n dice with f faces and a modifier m, decide whether a reported total S is reachable by checking if S minus m lies between n and n times f.	Easy2	MathImplementation	No attempts yet	2s	1024 MB	Judgeable
Clever InesReverse a column-by-column reading of an r x s grid (r at most s, r*s = n, r as large as possible) to recover the original message.	Easy2	ImplementationString+1	No attempts yet	1s	1024 MB	Judgeable
ClockGiven a clock time h and m, find the first moment the hour hand lands on the minute hand's mark, then print that clock time and the elapsed time.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
TimeGiven the departure and arrival times of three cars, find the shortest and longest trip durations and print them as hh:mm.	Easy2	ImplementationMath	No attempts yet	1s	1024 MB	Judgeable
TrianglesGiven N named points with integer coordinates, list every triple of points that is not collinear, with the names in input order.	Easy2	Brute forceGeometry	No attempts yet	1s	1024 MB	Judgeable
RectangleGiven a rectangle's perimeter in meters and centimeters and the centimeter difference d between its sides, output the two side lengths.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
I Thought of a NumberGiven a and b, find the starting number that becomes b after dividing by a, subtracting a, and repeating those two steps once more.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
FakirGiven the counts of gray, white, black, and spotted mice, find the fewest draws that guarantee at least one mouse of each color.	Easy2	ImplementationMath	No attempts yet	1s	1024 MB	Judgeable
Cutting Colored PaperGiven the area W of one half of a square sheet cut along its width, print the perimeter of the original square.	Easy2	MathImplementation	No attempts yet	0.5s	1024 MB	Judgeable
Rampant GrowthCount the ways to place exactly one plant per column in an r by c grid so that plants in adjacent columns sit in different rows, modulo 998244353.	Easy2	MathCombinatorics	No attempts yet	1s	2048 MB	Judgeable
Clock TowerGiven the minute M that the altered minute hand points to, find the true minute and print it with one decimal place.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Special TechnologyGiven student heights, find the greatest final height reachable when each student is hit at most once, printed modulo 10^9+7.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Watermelon GameGiven N and K cherries, find how many level N watermelons can be made by merging two equal-level fruits into the next level.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Malatang TanghuluGiven skewers with strawberry and grape counts and fixed insert amounts P and Q, decide whether every skewer can be balanced and print the insert counts.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Placing Game PiecesGiven a board N cells wide and M cells tall, count the unordered pairs of cells that touch each other diagonally.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
PE Is a Math SubjectGiven the two side lengths of a rectangular playground in meters, print the radius in centimeters of the largest circle that fits inside it.	Easy2	MathImplementation	No attempts yet	0.5s	1024 MB	Judgeable
I Want to Go to DIMIGO!Given a page range from A to B, find the fewest photos, where one photo can capture a single page or an open spread of pages 2k-1 and 2k.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Sejong's Time TravelGiven the current date and location and a target date and location, print the coordinates to enter, since the machine moves opposite to each entered change.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Rhythm GameGiven N measures with BPM changes at certain measures, compute the song's total play time in seconds, where each measure has 4 beats.	Easy2	ImplementationMath	No attempts yet	1s	1024 MB	Judgeable
DartboardGiven 20 dartboard scores in circular order, print whichever of Alice (aims at 20 and its two neighbors) or Bob (averages all sectors) has the higher expected score, or Tie.	Easy2	ArrayMath	No attempts yet	1s	1024 MB	Judgeable
Fractions are better when continuedGiven N, print the numerator of p_N, where p_0 = 1 and p_N = 1 / (1 + p_(N-1)), written in lowest terms.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Expected ErrorGiven a sudo password of length n, a slip after k correct characters with probability p%, pick the strategy (continue, backspace, or restart) with the lowest expected typing time.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Composed RhythmsGiven N, the task is to split N into groups of sizes 2 and 3 that sum to exactly N and print one valid decomposition.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Building PyramidsGiven n, the number of spheres on one edge of a tetrahedral stack, output the total number of spheres in the pyramid.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Expected EyesGiven n dice and the number of faces on each, print the expected value of the sum when all dice are rolled at once.	Easy2	Math	No attempts yet	4s	1024 MB	Judgeable
What Is a HumanGiven N, decide whether N is a multiple of 2024 that is at most 2024 times 100000, and print Yes or No.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Which Number Kind Is It?Given up to 100000 integers N up to 10^6, print O if N is odd, S if N is a perfect square, OS if both, and EMPTY otherwise.	Easy2	MathImplementation	No attempts yet	2s	1024 MB	Judgeable
Gahee and the Electricity Bill 1Given a power draw of a W and a usage time of m minutes per query, compute the bill at 105.6 won per kWh, truncated to an integer.	Easy2	MathImplementation	No attempts yet	1s	512 MB	Judgeable
Generalized FizzBuzzGiven n, a, and b, count how many times Fizz, Buzz, and FizzBuzz are printed in a generalized FizzBuzz run from 1 to n.	Easy2	MathImplementation	No attempts yet	1s	2048 MB	Judgeable
The Coin God GeonmoGiven a principal N and a loss percentage X, find the percentage rise needed from the reduced amount to return exactly to N.	Easy2	Math	No attempts yet	1s	1024 MB	Judgeable
Consolidating WindowsGiven two square window side lengths a and b, output the side length of one square whose area equals a squared plus b squared.	Easy2	Math	No attempts yet	1s	1024 MB	Judgeable
ChipsGiven k cans with n chips each, find the minimum and maximum number of minutes that can pass before Vasiliy takes an empty can.	Easy2	MathImplementation	No attempts yet	2s	2048 MB	Judgeable
Graphs and GraphsGiven a line Ax + By = C, add a directed edge from x to y for every integer point (x, y) with 1 to 10 on the line, then print each vertex's out-neighbors.	Easy2	Brute forceImplementation+1	No attempts yet	1s	1024 MB	Judgeable
Bitcoin HalvingGiven the initial reward R, the halving interval K, and a block number M, print the mining reward of block M.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Jjin Even NumberGiven N, count the N-digit Jjin Even Numbers (no leading zero, except 0 itself) modulo 10^9+7 for up to 100,000 queries.	Easy2	MathImplementation	No attempts yet	1s	1024 MB	Judgeable
Either, but Not BothCount the integers from 1 to N that are divisible by exactly one of A and B.	Easy2	MathImplementation	No attempts yet	2s	2048 MB	Judgeable
Hezardastan's Annual ReportGiven the page count of each chapter, find the fewest A4 sheets needed when every chapter starts on an odd page and no sheet mixes two chapters.	Easy2	MathImplementation	No attempts yet	1s	2048 MB	Judgeable
Divar's SalariesComputes each employee's monthly pay from wage x, total hours k, and holiday hours h, using 1.5x for hours past 140 and 2x for holiday hours.	Easy2	ImplementationMath	No attempts yet	1s	2048 MB	Judgeable
Defense ClockGiven the total service days N and completed days M, print the Defense Clock time in HH:MM, where 1440 minutes span the full service period, truncated to whole minutes.	Easy2	MathImplementation	No attempts yet	2s	1024 MB	Judgeable
I Flipped The Calendar...Given a year from 1970 to 2037, count the rows the twelve monthly calendar sheets need when each week starts on Monday.	Easy2	ImplementationMath	No attempts yet	2s	2048 MB	Judgeable
Sum of a SequenceGiven N and a minimum length L, find the shortest run of consecutive non-negative integers summing to N, or print -1 if none exists within length 100.	Easy3	MathBrute force+1	No attempts yet	2s	128 MB	Judgeable
DivisorsGiven all proper divisors of an unknown number N, compute N using the fact that the smallest and largest proper divisors multiply to N.	Easy3	MathNumber theory+1	No attempts yet	2s	512 MB	Judgeable
Guitar StringsBuy at least N guitar strings using packages of 6 or single strings from M brands at given prices, minimizing total cost.	Easy3	Brute forceGreedy+1	No attempts yet	2s	128 MB	Judgeable
Tournament Meeting RoundSimulate a single-elimination tournament where positions are halved each round to find when two specific players first face each other.	Easy3	SimulationMath+1	No attempts yet	1s	512 MB	Judgeable
Addition CycleSimulate a digit-transformation cycle on a two-digit number until it returns to the original value and count the steps.	Easy3	SimulationMath	No attempts yet	2s	128 MB	Judgeable
UnderprimeCount integers in a range whose total number of prime factors (with multiplicity) is itself a prime number.	Easy3	Number theoryMath+1	No attempts yet	2s	128 MB	Judgeable
Least Common Multiple of at Least Three NumbersGiven five distinct positive integers up to 100, find the smallest number divisible by at least three of them, essentially the minimum LCM over all triples.	Easy3	MathBrute force+2	No attempts yet	2s	128 MB	Judgeable
Strange MultiplicationGiven two large numbers as digit strings, compute the sum of all pairwise products of their digits, which equals the product of their digit sums.	Easy3	MathString+1	No attempts yet	2s	256 MB	Judgeable
Dice SumGiven three dice with sizes S1, S2, S3, find the sum value that occurs most often among all possible triples, choosing the smallest if tied.	Easy3	Brute forceMath+1	No attempts yet	2s	128 MB	Judgeable
Binary AdditionAdd two binary strings up to 80 digits long and print the sum in binary without leading zeros.	Easy3	StringMath+1	No attempts yet	2s	128 MB	Judgeable
Alphabet DiamondGiven a repeating diamond-pattern tile defined by N, print the characters inside a specified rectangular region of the infinite tiled plane.	Easy3	SimulationMath+1	No attempts yet	2s	128 MB	Judgeable
Lee-myeon and Im-hyeonClassify a number 1 to 2700 as Lee-myeon and/or Im-hyeon based on digit sum parity and prime factorization rules, then output one of four codes.	Easy3	Number theoryImplementation+1	No attempts yet	2s	128 MB	Judgeable
D-DayCompute the number of days between two calendar dates accounting for leap years, printing 'gg' if the gap reaches 1000 years or more.	Easy3	MathImplementation	No attempts yet	2s	128 MB	Judgeable
Decimal DigitSimulate long division of A by B to output the N-th digit after the decimal point.	Easy3	SimulationMath+1	No attempts yet	2s	128 MB	Judgeable
Missed CallSimulate an album of N songs with 5-second gaps and a phone ringing every D seconds to find the first ring Kangto can actually hear.	Easy3	SimulationImplementation+1	No attempts yet	2s	128 MB	Judgeable
Arithmetic ProgressionGiven a sequence S and starting value A0, find the smallest common difference d >= 0 of an arithmetic progression so that floor(A0+(i+1)d) equals S_i for every index.	Easy3	MathImplementation	No attempts yet	2s	128 MB	Judgeable
HockeyCount how many given points lie inside or on the boundary of a stadium shape formed by a rectangle and two semicircular ends.	Easy3	GeometryImplementation	No attempts yet	2s	128 MB	Judgeable
LotteryGiven N, M, K, compute the probability that two random M-subsets of 1..N share at least K numbers using the hypergeometric distribution.	Easy3	CombinatoricsMath+1	No attempts yet	2s	128 MB	Judgeable
Binary to Octal ConversionConvert a binary number with up to 1,000,000 digits into its octal representation.	Easy3	Bit manipulationMath+2	No attempts yet	1s	128 MB	Judgeable
Eumha Railway 998Find the point on the train's straight-line path where it comes closest to a given station, guaranteed to have integer coordinates.	Easy3	GeometryMath	No attempts yet	2s	128 MB	Judgeable
K-Sejun NumbersCount integers from 1 to N whose every prime factor is at most K, given N up to 100000 and K up to 100.	Easy3	MathNumber theory+1	No attempts yet	2s	128 MB	Judgeable
WalkingCompute the minimum time to walk from (0,0) to (X,Y) on a grid where straight moves cost W and diagonal moves cost S.	Easy3	MathGreedy	No attempts yet	2s	128 MB	Judgeable
Make It OneCompute the minimum number of divide-by-3, divide-by-2, or subtract-1 operations needed to reduce N to 1.	Easy3	Dynamic programmingMath	No attempts yet	0.15s	128 MB	Judgeable
Date Cycle CalculationFind the smallest year whose Earth, Sun, and Moon cycle counters, each resetting at fixed limits, match a given triple of values.	Easy3	SimulationMath+1	No attempts yet	2s	4 MB	Judgeable
DietGiven G, find all natural numbers a such that a^2 minus some natural number's square equals G, printing them in increasing order or -1 if none exist.	Easy3	MathNumber theory+1	No attempts yet	2s	128 MB	Judgeable
Guitar ConcertGiven up to 10 guitars each covering a subset of up to 50 songs, find the minimum number of guitars needed to play the maximum possible number of songs.	Easy3	Bit manipulationBrute force+1	No attempts yet	2s	128 MB	Judgeable
Maximum ProductSplit S into K positive integers as equal as possible to maximize their product, given S and K up to 100 and 20.	Easy3	MathGreedy	No attempts yet	2s	128 MB	Judgeable
Largest Lucky NumberGiven N up to 1,000,000, find the largest number no greater than N whose digits are only 4s and 7s.	Easy3	RecursionBrute force+1	No attempts yet	2s	256 MB	Judgeable
Count Numbers Made Only of 4 and 7Count integers between A and B (up to 1e9) whose digits are all 4s and 7s.	Easy3	Brute forceCombinatorics+2	No attempts yet	2s	128 MB	Judgeable
Lost ParenthesesGiven an arithmetic expression with only plus and minus signs, place parentheses to minimize the evaluated result.	Easy3	GreedyString+1	No attempts yet	2s	128 MB	Judgeable
Yongsik Goes to CampFor N bus schedules given by first departure, interval, and count, find the minimum wait until Yongsik can board any bus after arriving at time T, or -1 if none is available.	Easy3	SimulationMath+1	No attempts yet	2s	128 MB	Judgeable
Youngsik and Friends' Ball TossSimulate a ball being passed clockwise or counterclockwise by L seats depending on parity of catch count, counting throws until someone catches it M times.	Easy3	SimulationImplementation+1	No attempts yet	2s	128 MB	Judgeable
Modular ExponentiationCompute A raised to the power B modulo C efficiently using fast modular exponentiation.	Easy3	MathNumber theory+1	No attempts yet	0.5s	128 MB	Judgeable
Seongjun and ChocolateGiven chocolate and coffee doses with time-decaying effect radii, sum the positive radii (minimum 1) for each query time.	Easy3	SimulationBrute force+2	No attempts yet	1s	128 MB	Judgeable
Number of Trailing Zeros in a FactorialCount the trailing zeros of N! for N up to 500 by counting factors of 5.	Easy3	MathNumber theory+1	No attempts yet	2s	128 MB	Judgeable
Prime PalindromeFind the smallest number greater than or equal to N that is both a prime and a palindrome.	Easy3	MathBrute force+1	No attempts yet	2s	256 MB	Judgeable
Multiple of ThreeGiven a huge number as a digit string, repeatedly sum its digits until one digit remains, then report how many steps it took and whether the number is divisible by 3.	Easy3	StringMath+1	No attempts yet	2s	128 MB	Judgeable
Firework ShowGiven N firework periods and an end time C, count how many distinct seconds from 1 to C have at least one firework fired by any student.	Easy3	ArrayMath+1	No attempts yet	2s	128 MB	Judgeable
Extended Fibonacci NumbersCompute the sign and absolute value modulo 1e9 of the Fibonacci sequence extended to negative indices for a given n up to 1,000,000 in absolute value.	Easy3	MathImplementation	No attempts yet	2s	128 MB	Judgeable
Sum of Distinct NumbersGiven a sum S, find the largest number of distinct positive integers that can add up to exactly S.	Easy3	MathBinary search+1	No attempts yet	2s	128 MB	Judgeable
Logic ProfessorGiven N statements each claiming exactly x of them are true, find the largest consistent count of true statements or -1 if none works.	Easy3	Brute forceMath	No attempts yet	2s	128 MB	Judgeable
Encryption KeyDetermine for each large number S whether all its prime factors exceed one million, using trial division up to that bound.	Easy3	Number theoryMath+1	No attempts yet	2s	128 MB	Judgeable
Safe Password CheckGiven a number P equal to the product of two primes and a threshold K, decide if both primes are at least K, otherwise output the smaller prime.	Easy3	Number theoryMath+1	No attempts yet	2s	256 MB	Judgeable
Broken OdometerConvert an odometer reading that skips the digit 4 back into the real distance traveled, using a base-9-like digit mapping.	Easy3	MathImplementation+1	No attempts yet	0.5s	128 MB	Judgeable
01 TilesCount length-N binary strings tileable by '1' and '00' pieces, modulo 15746, which reduces to a Fibonacci recurrence.	Easy3	Dynamic programmingMath	No attempts yet	0.75s	256 MB	Judgeable
Tower of HanoiPrint the minimum move count for Tower of Hanoi with N disks, using big-integer count for N up to 100 and the explicit move sequence when N is at most 20.	Easy3	RecursionMath+1	No attempts yet	6s	128 MB	Judgeable
TriangleGiven three points, classify the triangle they form as degenerate, equilateral, isosceles or scalene, and further by its largest angle type.	Easy3	GeometryImplementation+1	No attempts yet	2s	128 MB	Judgeable
Find Prime NumbersPrint all prime numbers between two given bounds M and N, one per line, using an efficient sieve up to 1,000,000.	Easy3	MathNumber theory+1	No attempts yet	2s	256 MB	Judgeable
Counting Consecutive SumsCount the number of ways to express a given natural number N as a sum of one or more consecutive natural numbers.	Easy3	MathNumber theory	No attempts yet	2s	32 MB	Judgeable
RoundingGiven an integer up to 99,999,999, repeatedly round its digits at increasing place values (tens, hundreds, etc.) using standard rounding rules and print the final result.	Easy3	MathImplementation+1	No attempts yet	2s	128 MB	Judgeable
Completing a Magic SquareGiven a 3x3 magic square with up to three cells erased (marked 0), fill in the missing positive integers so all rows, columns, and diagonals share the same sum.	Easy3	MathMatrix+1	No attempts yet	2s	128 MB	Judgeable
Negative BinaryConvert a given decimal integer into its base -2 (negabinary) representation.	Easy3	MathImplementation	No attempts yet	2s	128 MB	Judgeable
PebblesGiven N pebbles to place on grid points, compute the minimum possible perimeter of the smallest bounding rectangle covering all of them.	Easy3	MathImplementation	No attempts yet	1s	128 MB	Judgeable
StatisticsGiven N odd integers, compute and print the rounded mean, median, mode (second smallest if tied), and range.	Easy3	ArraySorting+1	No attempts yet	2s	256 MB	Judgeable