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

    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
         long kth_therm = (long)((long)k-1)*((long)k)/2L + 1L;
        long fkth_1_therm = (2L*kth_therm)-1L;
      
        long sum = 0;
        long numValue = fkth_1_therm;
        
        for(int i=0; i < k; i++)
        {
            
            sum += numValue;
            numValue += 2;
        }
        
       // Console.WriteLine("kth: " + kth_therm);
       // Console.WriteLine("fkth: " + fkth_1_therm);
        
        return sum;
    }

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