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