#include<cstdio>
typedef long long ll;
int main()
{
    int n,k;
    while(scanf("%d%d",&n,&k) && n+k){
        ll ans=1;
        if(k>n/2) k=n-k;
        for(int i=1;i<=k;++i)
            ans=ans*(n-i+1)/i;
        printf("%lld\n",ans);
    }
    return 0;
}