#include <bits/stdc++.h>
using namespace std;
const int maxn = 300005;
long long n;
int main() {
  while (scanf("%lld", &n) == 1) {
    long long ans =
        (n * (n + 1) * (2 * n + 1)) / 6 - ((3 + n) * (n - 2)) / 2 - 5;
    printf("%lld\n", ans);
  }
}
