#include <iostream>

using namespace std;

int main()
{
    long int i, k, terms = 0, initial = 0, sum = 0;
    cin >> k;
    for(i = 0; i < k; i++)
        terms = terms + i;
    initial = 1 + terms * 2;
    for(i = 0; i < k; i++)
    {
        sum = sum + initial;
        initial += 2;
    }
    cout << sum;
    return 0;
}