题解

#include <bits/stdc++.h>
using namespace std;
#define int unsigned long long
int lst[16] = {1,0};
signed main()
{
    int N;
    cin >> N;
    for(int i = 2;i <= N;i++)
    {
        lst[i] = (lst[i-1]+lst[i-2])*(i-1);
    }
    cout << lst[N];
    return 0;
}