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

    static Dictionary<int, long> cache = new Dictionary<int, long>();
    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        long result;
        if (!cache.TryGetValue(k, out result))
        {
        
            long kk = k - 1;
            long startIndex = (kk * (kk + 1)) / 2;
            //Console.WriteLine("si"+startIndex);
            
            long b = startIndex*2 + 1;
            //Console.WriteLine("b"+b);
            result = b * k + (kk * (kk + 1));
        
            cache[k] = result;
        }
        return result;
        
    }

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