#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  int dp[4001];
  dp[0] = 1;
  for (int i = 0; i < 4000; i++) {
    dp[i + 1] = dp[i] + (i + 2) * (i + 3) / 2;
  }
  while (cin >> n) {
    cout << dp[n] << endl;
  }
  return 0;
}
