using System;

public static class Geometry

{

    public static double SquarePerimeter(double a)

    {

        return 4 * a;

    }

    public static double SquareArea(double a)

    {

        return a * a;

    }

    public static double RectangleArea(double a, double b)

    {

        return a * b;

    }

    public static double RectanglePerimeter(double a, double b)

    {

        return 2 * (a + b);

    }

    public static double CircleArea(double r)

    {

        return 2 * Math.PI * r; 

    }

}

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

}