problem solution

#include<bits/stdc++.h>

using namespace std;

int main() {
  unsigned long long int n, total, ans;
  cin >> n;
  if(n == 0) cout << 1 << "\n";
  else {
    total = ( n * ( n + 1 ) ) / 2;
    ans = (( 6 * total ) + 1 );
    cout << ans << "\n";
  }
}