#include<iostream>
#include<cmath>
#include<algorithm>
#include<string>
#include<map>
using namespace std;
long long sum(int n) {
    if (n == 1) {
        return 1;
    }
    return n * sum(n - 1);
}
int main() {
    int n;
    long long num = 0;
    cin >> n;
    for (int i = 1;i <= n;i++) {
        num += sum(i);
    }
    cout << num;
    return 0;
}