#include <bits/stdc++.h>
using namespace std;
int fastMax(int x, int y) { return (((y - x) >> (32 - 1)) & (x ^ y)) ^ y; }
int fastMin(int x, int y) { return (((y - x) >> (32 - 1)) & (x ^ y)) ^ x; }
void solve() {
  long long int n;
  cin >> n;
  set<pair<long long int, pair<long long int, long long int>>> s;
  long long int ans = 6;
  for (int i = (4); i <= (n); ++i) {
    ans += (i - 1) * i;
  }
  cout << ans << endl;
}
signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  long long int t;
  t = 1;
  while (t--) solve();
}
