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

   static long sumOfGroup(long k) {
       // Return the sum of the elements of the k'th group.
            long sum = 0;
       long val=0;
            val = (k * (k - 1)) + 1;            
            for (long i = 0; i < k; i++)
            {
              sum = sum + val + (2 * i);               
            }
            return sum;
    }

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