#include <bits/stdc++.h>
using namespace std;
int main() {
  unsigned long long k;
  cin >> k;
  if (k == 1) {
    cout << 6 << endl;
  } else {
    unsigned long long ans = ((2 * k + 1) * (2 * k + 1) + 1) / 2 + ((2 * k - 1) * (2 * k - 1) + 1) / 2;
    cout << ans << endl;
  }
  return 0;
}