#include <bits/stdc++.h>

using namespace std;

int main() {
    int n;
    int T;
    int sum = 0;
    cin >> n;
    for (int i = 1; i <= n; i++) {
        T = 1;
        for (int j = 1; j <= i; j++) {
            T *= j;
        }
        sum += T;
    }
    cout << sum << endl;
    return 0;
}