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 kk = ((long)(k-1))*(k-2)/2+(k-1)+1;
        kk = 2*kk-1;
        long summ = 0;
        for(int i = 0; i < k; i++)
        {
            summ += kk;
            kk+=2;
        }
        return summ;
    }

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