#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define Min(a,b) (a<=b)? a : b

ll nCr(ll n, ll r)
{
    ll f[n + 1];
    f[0] = 1;
    for (ll i = 1; i <= n; i++)
        f[i] = i * f[i-1];
    return f[n] / f[r] / f[n-r];
}

int main()
{
    ll n,r,m;
    while (cin >> n >> r)
    {
        cout << nCr(n, Min(r,n-r)) << endl;
    }
    return 0;
}