#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (int)n; i++)
using ll = long long;

int main(){
  ll k;
  cin >> k;
  cout << (k*2+1)*(k*2+1) - (k*4-1) << endl;
  return 0;
}