#include <bits/stdc++.h>
using namespace std;
int main(){
  int N, M;
  cin >> N >> M;
  vector<vector<long long>> S(N + 1, vector<long long>(N + 1, 0));
  S[0][0] = 1;
  for (int i = 1; i <= N; i++){
    for (int j = 1; j <= i; j++){
      S[i][j] = S[i - 1][j - 1] + S[i - 1][j] * j;
    }
  }
  if (M > N){
    cout << 0 << endl;
  } else {
    long long ans = S[N][M];
    for (int i = 1; i <= M; i++){
      ans *= i;
    }
    cout << ans << endl;
  }
}