source_code: import java.util.Scanner;
  
  public class AlexAndARhombus {
  	public static void main(String args[])
  	{
  		Scanner sc=new Scanner(System.in);
  		int n=sc.nextInt();
  		System.out.println(n*n+(n-1)*(n-1));
  		sc.close();
  	}
  
  }
  