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

    static long sumOfGroup(int k) {
    long total = 0;
    long startingNum = 0;
        for(int i = k - 1; i > 0; i--)
        {
            startingNum += i;
        }
    
        startingNum = startingNum * 2 + 1;
        
        for(int i = 0; i < k; i++)
        {
            total += startingNum;
            startingNum += 2;
        }
                
        return total;
    }

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