POJ 2249

#include<stdio.h>longlong sum;int main(){int k,n,m;while(~scanf("%d%d",&n,&m)&&(n!=0||m!=0)){sum =1;m = m<(n-m)?m:n-m;for(k =1;k <= m;k++)sum =(sum*(n-m+k))/k;printf("%lld\n",sum);}return0;}