1278. Binomial Showdown

单点时限: 2.0 sec

内存限制: 256 MB

In how many ways can you choose k elements out of n elements, not taking order into account?

Write a program to compute this number.

输入格式

The input will contain one or more test cases.

Each test case consists of one line containing two integers n (n>=1) and k (0<=k<=n).

Input is terminated by two zeroes for n and k.

输出格式

For each test case, print one line containing the required number. This number will always fit into an integer, i.e. it will be less than 2^31.

Warning: Don’t underestimate the problem. The result will fit into an integer - but if all intermediate results arising during the computation will also fit into an integer depends on your algorithm. The test cases will go to the limit.

样例

Input
4 2
10 5
49 6
0 0
Output
6
252
13983816

21 人解决,35 人已尝试。

27 份提交通过,共有 148 份提交。

5.7 EMB 奖励。

创建: 12 年,11 月前.

修改: 2 年,10 月前.

最后提交: 3 月,3 周前.

来源: Ulm Local 1997

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