50pts求调

#include <bits/stdc++.h>
#define ll long long
using namespace std;
ll factorial(ll n) {
	/*if (n < 2) return 1;
	else return (n * factorial(n - 1));*/
	ll sum = 1;
	for (int i = 1; i <= n; i++) {
		sum = sum * i;
	}
	return sum;
}
int main() {
	ll a;
	cin >> a;
	long long sum = 0;
	for (int i = 1; i <= a; i++) {
		sum += factorial(i);
	}
	cout << sum;
	return 0;
}