Backward Digit Sums

시간 제한1초메모리 제한1024 MB

요약

N과 목표 합이 주어질 때, 인접한 수를 계속 더해 하나의 수가 되는 과정의 결과가 목표 합이 되는 1..N의 순열 중 사전순으로 가장 앞선 것을 찾는다.

난이도: 보통10점 중 4점
유형: 백트래킹, 조합론, 완전 탐색, 재귀
정답자: 아직 제출이 없습니다

문제

FJ and his cows enjoy playing a mental game. They write down the numbers from 1 to N (1 ≤ N ≤ 10) in a certain order and then sum adjacent numbers to produce a new list with one fewer number. They repeat this until only a single number is left. For example, one instance of the game (when N=4) might go like this:

    3   1   2   4

      4   3   6

        7   9

         16

Behind FJ's back, the cows have started playing a more difficult game, in which they try to determine the starting sequence from only the final total and the number N. Unfortunately, the game is a bit above FJ's mental arithmetic capabilities.

Write a program to help FJ play the game and keep up with the cows.

입력

Line 1: Two space-separated integers: N and the final sum.

출력

Line 1: An ordering of the integers 1..N that leads to the given sum. If there are multiple solutions, choose the one that is lexicographically least, i.e., that puts smaller numbers first.

예제1

예제 1
입력
```
4 16
```
예상 출력
```
3 1 2 4
```