#include <bits/extc++.h>
using namespace std;
using ll = long long;
#define REP(i,n) for(int i=0;i<int(n);i++)
#define FOR(i,a,b) for(int i=a;i<=int(b);i++)
#define ALL(x) x.begin(),x.end()
#define INF INT_MAX
#define INFL LLONG_MAX

int main() {

  vector<vector<ll>> x(20, vector<ll>(20));
  vector<vector<ll>> am(20, vector<ll>(20));

  x[0][0] = 1;

  vector<ll> n1(16);
  n1[0] = 1;
  REP(i, 15) {
    n1[i+1] = n1[i] * (i+1);
  }

  REP(i, 15) {
    FOR(j, 0, i) {
      x[i+1][j+1] += x[i][j];
      x[i+1][j] -= i * x[i][j];
    }
  }

  FOR(i, 1, 15) {
    am[i][i] = n1[i];
    FOR(j, 1, i-1) {
      FOR(k, 1, 15) {
        am[i][k] -= x[i][j] * am[j][k];
      }
    }
  }
  ll n, m;

  cin >> n >> m;

  if(n == 0) cout << "NaN";
  else if(m > n) cout << 0;
  else cout << am[n][m];

  

  return 0;
}