Description

In mathematics, the binomial theorem is an important formula giving the expansion of powers of sums. Its simplest version states that


for any real or complex numbers x and y, and any nonnegative integer n. The binomial coefficient appearing in (1) may be defined in terms of the factorial function n!:


For example, here are the cases where 2 ≤ n ≤ 5:



History

This formula and the triangular arrangement of the binomial coefficients are often attributed to Blaise Pascal, who described them in the 17th century. But they were known to many mathematicians who preceded him: 4th century B.C. Greek mathematician Euclid, 3rd century B.C. Indian mathematician Pingala, 11th century Persian mathematician Omar Khayyám, and 13th century Chinese mathematician Yang Hui all derived similar results.

There have an other formula compute C(n,k):
C(n,k)=C(n-1,k-1)+C(n-1,k)

Your task is this formula above compute C(n,k).

Input

多组测试数据，每组提供n和k。以0,0结束。

Output

C(n,k)的结果。

Sample Input


2 1
3 1
4 4
10 6
0 0

Sample Output


2
3
1
210

怎么没人帮我啊?高手们啊!

你说你需要帮助了么

麻烦高手们帮我搞定这个题好吗,谢谢

原来是二项式定理里的系数求解问题啊,
用递归吧.

麻烦高手给出源代码,谢谢了

试试这个看行么
#include<stdio.h>
int main(){
    int n,k,i;
    double com;
    int c;
    while(scanf("%d%d",&n,&k)){
         if(n+k==0)
           break;
         com=1;
         if(k>n/2)
            k=n-k;
         for(i=1;i<=k;i++){
            com*=(n-i+1);
            com/=i;
         }
         c=int(com);
         printf("%d\n",c);
    }
    return 0;
}

多谢了朋友!非常感谢