#include<bits/stdc++.h>
using namespace std;

int main()
{
    long long int n,r,k,i,j,a,b,c,ans,ans1,ans2;
    while(cin>>n>>r && n||r)
    {

        a=min(r,n-r);
        ans1=1,ans2=1;
        b=n-a+1;
        for(i=b,j=1;i<=n&&j<=a;i++,j++)
        {
           ans1*=i;
           ans2*=j;
           if(ans1%ans2==0)
           {
               ans1/=ans2;
               ans2=1;
           }
        }
        cout<<ans1<<endl;
    }
    return 0;
}