#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  while (cin >> n) {
    long long int ans = 1;
    long long int ans_sa = 3;
    long long int ans_sa_pls = 3;
    for (int i = 0; i < n; i++) {
      ans += ans_sa;
      ans_sa += ans_sa_pls;
      ans_sa_pls++;
    }
    cout << ans << endl;
  }
}
