B

#include <cstdio>
#include <iostream>


using namespace std;

int main() {
    int n, i;
    long long sum;
    while(cin >> n) {
        sum = 0;
        for(i = 0; i < (n-1); i++) sum += ((n-i-1) + i * (n-i-1));
        sum += n;
        cout << sum << "\n";
    }
    return 0;
}