#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int a, b, c, i, j, k, n, m, t, x, y, z, sum = 0, ans = 0, id, cnt;
  cin >> n;
  i = 2;
  j = 3;
  for (int ii = 3; ii <= n; ii++) {
    k = i * j;
    sum += k;
    i++;
    j++;
  }
  cout << sum << endl;
  return 0;
}
