#include <bits/stdc++.h>
using namespace std;
void solve() {
  int n, ans;
  cin >> n;
  ans = ((n - 1) * (n - 1) * 2) + ((2 * n) - 1);
  cout << ans << "\n";
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  while (t--) solve();
  return 0;
}
