gNumber Game (Large)
Time limit5sMemory limit512 MB
Players alternate removing one prime factor entirely from N, and whoever faces a number with digit sum 1 or prime loses; report the winner under optimal play.
- Level
Medium7 of 10
- Topics
- Game theory, Number theory, Brute force
- Solved
- No attempts yet
Problem
A number is a gNumber if the sum of its digits has no positive divisor other than 1 and itself. The digit sum of 1 is 1, and 1 has no divisor other than 1 and itself, so 1 is a gNumber.
Laurence and Seymour play a game with gNumbers. Someone who is not playing first picks a starting number . The two players then take turns.
On a turn, the player checks whether the current number is a gNumber. If it is, that player loses right there. Otherwise the player picks one prime factor of and divides by repeatedly until no longer divides it. For example, if the current number is 72, the player can pick 2 and divide down to 9, or pick 3 and divide down to 8. The result becomes the new current number and the turn passes to the opponent.
Laurence always moves first. Given the starting number , report who is certain to win when both players play optimally.
Input
The first line contains the number of test cases . Each of the next lines contains one starting number .
Output
For each test case, print one line in the form Case #x: y, where is the test case number starting from 1 and is the winner's name, either Laurence or Seymour.
Constraints
Hint
For the digit sum is 2, and 2 has no divisor other than 1 and itself, so 2 is a gNumber. Laurence loses immediately and Seymour wins. The same happens for .
For the digit sum is 4, and 4 has the divisor 2 besides 1 and 4, so 4 is not a gNumber. The only prime factor of 4 is 2, so Laurence must pick 2 and divide until 1 is left. Seymour starts his turn on 1, which is a gNumber, so Seymour loses and Laurence wins.