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 next = (k - 1) * k / 2;
        //Console.WriteLine(next);
        long cur = 2 * next + 1;
        //Console.WriteLine(cur);
        long sum = k * (cur + k - 1);
        return sum;
    }

    static void Main(String[] args) {
        long k = Convert.ToInt64(Console.ReadLine());
        long answer = sumOfGroup(k);
        Console.WriteLine(answer);
    }
}