蓝桥

[落尘594]

#include <iostream>
using namespace std;

#define int long long
int C(int n, int m) {
  int res = 1;
    for (int i = 1; i <= m; i++) {
        res = res * (n - i + 1) / i;
    }
    return res;
}

int D[25];
signed main()
{
  
  D[0] = D[1] = 0;
  D[2] = 1;
  for (int i = 3; i <= 14; i++) {
    D[i] = (i - 1) * (D[i - 1] + D[i - 2]);
  }
  cout << C(28, 14) * D[14] << "\n";
  return 0;
}