using System;

public class Program

{

    public abstract class Shape

    {

        private int numSides;

        readonly int newSides;

​

        public Shape(int numSides)

        {

            this.numSides = numSides;

        }

​

        public abstract string GetPerimeter();

​

        public abstract double GetArea();

​

    }

    public class IsoscelesTriangle : Shape

    {

        private double side;

        private double height;

​

​

        public override double GetArea()

        {

            double area = (side * height) / 2;

            return area;

        }

        public override GetArea():

    }

    public class Rectangle : Shape

    {

        public Rectangle(double width, double height) 

        {

            this.width = width;

            this.height = height;

        }

​

        public double getArea() 

        {

            return width * height;

        }

​

        public double getPerimeter() 

        {

            return 2 * (width + height);

        }

​

    }

​

        public static void Main()

        {

            Console.WriteLine("Hello World");

        }

}