#include <bits/stdc++.h>   using namespace std;   const long long MOD = (long long)1e9 + 7;   const int inf = (int)1e9 + 7;   const double eps = 1e-7;   const double pi = 3.14159265359;   const int N = (int)1e4;   const int K = 4;   long long n, k;   long long dp[N][K];   signed main() {     scanf( %lld%lld , &n, &k);     if (k == 1) printf( 1 );     if (k == 2) printf( %lld , n * (n - 1) / 2 + 1);     if (k == 3) printf( %lld , n * (n - 1) * (n - 2) / 3 + n * (n - 1) / 2 + 1);     if (k == 4)       printf( %lld , n * (n - 1) * (n - 2) * (n - 3) / 8 * 3 +                          n * (n - 1) * (n - 2) / 3 + n * (n - 1) / 2 + 1);     return 0;   }   