171/B - Star

///https://trello.com/c/UUGJrJ7N/29-https-codeforcescom-problemset-problem-171-b
///https://codeforces.com/problemset/problem/171/B

#include <iostream>
#define ll long long
using namespace std;

int main ()
{
    ll n;
    cin>>n;
    cout<< (2*n-1)*(2*n-1) + 2*n*(n-1);

    return 0;
}