using System.Numerics;
using System;


class Solution
{

    static long sumOfGroup(long k)
    {
        long n = k * (k - 1) / 2;
        long min = 2 * n + 1;
        return ((min * k) + k * (k - 1)) ;
    }

    static void Main(String[] args)
    {
        long k = Convert.ToInt32(Console.ReadLine());
        long answer = sumOfGroup(k);
        Console.WriteLine(answer);
    }
}