using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {
    static int sumbis(int k){
        if(k==1) return 1;
        return k + sumbis(k-1);
    }
    static long sumOfGroup(int k) {
        // Return the sum of the elements of the k'th group.
        long res=0;
        List<int> oddbis = new List<int>();
        for(int i=1; i<=sumbis(k)*2; i=i+2){
                oddbis.Add(i);
            }
        for(int i=oddbis.Count-1;i>oddbis.Count-1-k;i--){
                res+=oddbis[i];
            }
            
        return res;
    }

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