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 nth = (k * (1+k)) / 2;
        long odd = 1 + ( 2 * (nth - 1));
        long result = 0;
        if(nth == k)
            result = 1;
        else{
        for(long i = nth; i > (nth - k); i--){
            result = result + odd;
            odd = odd - 2;
        }
        }
        return result;
    }

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