#include <bits/stdc++.h>

using namespace std;

long sum(long k) {
  // returns 1 + 2 + 3 + ... + k
  return k*(k+1) / 2;
}

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
  // the kth group contains k elems
  long s = 2 * sum(k) - 1;
  long res = 0;
  for(long i = 0; i < k; ++i) {
    res += s;
    s -= 2;
  }
  return res;
}

int main() {
    int k;
    cin >> k;
    long answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}