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 n = (k + 1) * k / 2;
        long n1 = (k - 1) * k / 2;
        return (n ) * (n ) - (n1 ) * (n1 );
    }

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