using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        Console.WriteLine("Enter r");

        double r = double.Parse(Console.ReadLine());

        double x = Math.PI;

        double y = Math.Pow(r,2);

        double ca = x*y;

        Console.WriteLine("Circle area:{0:f3}*{1}={2:f4}",x,y,ca);

        Console.ReadLine();

    }

}