#include <bits/stdc++.h>
using namespace std;
int main(){
    int n,sum,t;
    cin >> n;
    for(int i = 1;i <= n;i++){
        for(int j = i;j >= 1;j--){
            t *= j;
        }
        sum += t;
        t = 1;  
    }
    cout << sum;
    return 0;
}