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

    static long sumOfGroup(int k) {
        var n = (k - 1L) * k + 1L;
        return (n + n + 2L * (k - 1L)) * k / 2L;
    }

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