using System;

namespace PolymorphismApplication

{

   class Shape 

   {

      protected int width, height;

      public Shape( int a=0, int b=0)

      {

         width = a;

         height = b;

      }

      public virtual int area()

      {

         Console.WriteLine("Parent class area :");

         return 0;

      }

   }

   class Rectangle: Shape

   {

      public Rectangle( int a=0, int b=0): base(a, b)

      {

​

      }

      public override int area ()

      {

         Console.WriteLine("Rectangle class area :");

         return (width * height); 

      }

   }

   class Triangle: Shape

   {

      public Triangle(int a = 0, int b = 0): base(a, b)

      {

      }

      public override int area()

      {

         Console.WriteLine("Triangle class area :");

         return (width * height / 2); 

      }

   }

   class Caller

   {

      public void CallArea(Shape sh)

      {

         int a;

         a = sh.area();

         Console.WriteLine("Area: {0}", a);

      }

   }  

   public class Tester

   {

      public static void Main(string[] args)

      {

         Caller c = new Caller();

         Rectangle r = new Rectangle(10, 7);

         Triangle t = new Triangle(10, 5);

         c.CallArea(r);

         c.CallArea(t);

         Console.ReadLine();

      }

   }

}