source_code: import java.io.*;
  import java.lang.*;
  import java.util.*;
  public class alex
  {
      public static void main(String[] args)throws IOException
      {
          Scanner sc=new Scanner(System.in);
          int n=sc.nextInt();int sum=1;
          for(int i=1;i<=n;i++)
          {
              sum=sum+(4*(i-1));
          }
          System.out.println(sum);
      }
  }