using System;

​

abstract class Shape

{

    public abstract double GetArea();

    public abstract double GetPerimeter();

}

​

class Circle:Shape

{

    public double radius;

    public const double PI = Math.PI;

    public Circle(double radius)

    {

        this.radius = radius;

    }

    public override double GetArea()

    {

        return PI * radius * radius;

    }

    public override double GetPerimeter()

    {

        return 2 * PI * radius;

    }

}

​

class Rectangle:Shape

{

    public double width;

    public double height;

    public Rectangle (double width, double height)

    {

        this.width = width;

        this.height = height;

    }

    public override double GetArea()

    {

        return  width * height;

    }

    public override double GetPerimeter()

    {

        return 2 * ( width + height);

    }

}

​

public class Program

{

    public void Main()

    {

        Circle myCircle = new Circle(5);

        Rectangle myRectangle = new Rectangle(5, 10);

​

        Console.WriteLine(myCircle.GetArea());

        Console.WriteLine(myCircle.GetPerimeter());

        Console.WriteLine(myRectangle.GetArea());

        Console.WriteLine(myRectangle.GetPerimeter());

    }

}