#include <iostream>
using namespace std;
int main(){
	int n, s;
    long long sum = 0; 
	cin >> n;
	for(int i = 1; i <= n; i++){
		s = 1;
		for(int j = 1; j <= i; j++){
			s *= j;
		}sum += s;
	}cout << sum;
	return 0;
}

代码在此