#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  unsigned long long ans, x, n;
  cin >> n;
  x = (n * (n + 1)) / 2;
  ans = (6 * x) + 1;
  cout << ans << endl;
  return 0;
}
