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

    static long sumOfGroup(int k) {
        var seed = (long)k * (k - 1) + 1;

        return Enumerable.Repeat(seed, k)
                .Select((n, i) => n + i * 2)
                .Sum();
    }

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