#include <bits/stdc++.h>

using namespace std;

int jiecheng(int n) {
    int result = 1;
    for (int i = 1; i <= n; ++i) {
        result *= i;
    }
    return result;
}

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