using System;

public abstract class Shape

{ public abstract double CalculatePerimeter();

  public abstract double CalculateArea();

 public virtual string Draw()

 {return "Drawing "; }

} 

 public class Circle : Shape

 { public double radius;

  public Circle(double rad)

  { this.radius = rad; }

  public override double CalculatePerimeter()

  { return 2*Math.PI* this.radius; }

  public override double CalculateArea()

  { return Math.PI*this.radius* this.radius; }

  public sealed override string Draw ()

  { return base.Draw() + "Circle"; }

}  

  public class Rectangle : Shape

  { public double sideA; public double sideB;

    public Rectangle(double sidea, double sideb)

      { this.sideA = sidea; this.sideB = sideb; }

    public override double CalculatePerimeter()

      { return this.sideA * 2+ this.sideB*2; }

    public override double CalculateArea()

      { return this.sideA * this.sideB; }

    public sealed override string Draw()

      { return base.Draw() + "Rectangle"; }

  }

      public class Program

{

    public static void Main()

    {

        //Shape shape = new Shape(); // Грешка при компилиране 

        Shape circle = new Circle(4); // полиморфизъм Circle circle = new Circle (5);

        Console.WriteLine(circle.Draw());

        Console.WriteLine(circle.CalculatePerimeter());

        Shape rectan=new Rectangle(2,3.3);

        Console.WriteLine(rectan.Draw());Console.WriteLine(rectan.CalculatePerimeter());

        Console.WriteLine(rectan.CalculateArea());

    }

    }