题目1451：不容易系列之一

#include <iostream>
#include <algorithm>
#include <queue>
#include <vector>
#include <cstring>
#include <string>
#include <string.h>
#include <stdio.h>
#include <cmath>
#include <map>
#include <functional>
#include <set>
using namespace std;
//1451
long long int ans[21];
int main(){
    int n;
    ans[1]=0;
    ans[2]=1;
    for(int i=3;i<21;i++)
        ans[i]=(i-1)*ans[i-1]+(i-1)*ans[i-2];
    while(cin>>n){
        cout<<ans
<<endl;
    }
    return 0;
}
/**************************************************************
    Problem: 1451
    User: cust123
    Language: C++
    Result: Accepted
    Time:0 ms
    Memory:1520 kb
****************************************************************/