using System;

public class Program

{

    public  interface Shape

{

​

​

            void CalculateArea();

​

        }

​

        class Triangle : Shape 

​

        {

​

            private double b = 5.0;

            private double h = 7.0;

            public void CalculateArea() 

​

            {

​

                Console.WriteLine(0.5 * b * h);

​

            }

​

        }

​

        class Rectangle : Shape 

​

        {

​

            private double x = 4;

            private double y = 8;

            public void CalculateArea() 

            {

                Console.WriteLine(x * y);

            }

        }

    public static void Main()

    {

        Shape triangle = new Triangle(); 

        triangle.CalculateArea(); 

        Shape rectangle = new Rectangle();  

​

        rectangle.CalculateArea();

    }

​

}