import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    static long sumOfGroup(long k) {
       
             
               long  s=k*(k-1)+1,sum=0;
       // System.out.println(s);
                for(int i=0;i<k;i++)
                {
                   sum+=(s);
                   s+=2;
                        
                }
                  return sum;
                   }
    
    

    public static void main(String[] args) {
            Scanner in = new Scanner(System.in);
            long k = in.nextLong();
            long answer = sumOfGroup(k);
            System.out.println(answer);
            in.close();
       }

}