using System;

public abstract class Shape

{

    private string myId;

    public Shape(string s)

    {

        Id = s;  

    }

    public string Id

    {

        get

        {

            return myId;

        }

        set

        {

            myId = value;

        }

    }

    public abstract double Area

    {

        get;

    }

    public override string ToString()

    {

        return Id + " Area = " + string.Format("{0:F2}", Area);

    }

}

public class Square : Shape

{

    private int mySide;

    public Square(int side, string id)

        : base(id)

    {

        mySide = side;

    }

    public override double Area

    {

        get

        {

            // Given the side, return the area of a square:

            return mySide * mySide;

        }

    }

}

public class Circle : Shape

{

    private int myRadius;

    public Circle(int radius, string id)

        : base(id)

    {

        myRadius = radius;

    }

    public override double Area

    {

        get

        {

            // Given the radius, return the area of a circle:

            return myRadius * myRadius * System.Math.PI;

        }

    }

}

public class Rectangle : Shape

{

    private int myWidth;

    private int myHeight;

    public Rectangle(int width, int height, string id)

        : base(id)

    {

        myWidth = width;

        myHeight = height;

    }

    public override double Area

    {

        get

        {

            // Given the width and height, return the area of a rectangle:

            return myWidth * myHeight;

        }

    }

}

public class TestClass

{

    public static void Main()

    {

        Shape[] shapes =

         {

            new Square(5, "Square #1"),

            new Circle(3, "Circle #1"),

            new Rectangle( 4, 5, "Rectangle #1")

         };

        System.Console.WriteLine("Shapes Collection");

        foreach (Shape s in shapes)

        {

            System.Console.WriteLine(s);

        }

        Console.ReadLine();

    }

}