using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {

    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        long first = 0,total = 0;
        first = k *  (k - 1) + 1;
        total = first + next(first,1,k);
        return total; 
    }
    static long next(long f, long i, long k)
    {
        if(i == (k-1))
            return f + 2*i;
        else 
            return f + (2 * i) + next(f,i+1,k);
    }
    static void Main(String[] args) {
        int k = Convert.ToInt32(Console.ReadLine());
        long answer = sumOfGroup(k);
        Console.WriteLine(answer);
    }
}