using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Task1
{
    class Program
    {
        static void Main(string[] args)
        {
            RightTriangle rightTriangle = new RightTriangle();

            Console.WriteLine("Area of Right Triangle is " + rightTriangle.GetArea() + "units");

            Console.WriteLine();

            Rectangle rectangle = new Rectangle();

            Console.WriteLine("Area of Right Triangle is " + rectangle.GetArea() + "units");
        }
    }

    abstract class Shape
    {
        public double x, y;

        abstract public double GetArea();
    }
    class RightTriangle : Shape
    {
        public override double GetArea()
        {
            double area;

            Console.WriteLine("Right Triangle\n");

            Console.Write("Value of Base : ");
            x = Convert.ToDouble(Console.ReadLine());

            Console.Write("Value of Perpendicular : ");
            y = Convert.ToDouble(Console.ReadLine());

            area = 0.5 * x * y;

            return area;
        }
    }
    class Rectangle : Shape
    {
        public override double GetArea()
        {
            double area;

            Console.WriteLine("Reactangle\n");

            Console.Write("Value of Base : ");
            x = Convert.ToDouble(Console.ReadLine());

            Console.Write("Value of Perpendicular : ");
            y = Convert.ToDouble(Console.ReadLine());

            area = 0.5 * x * y;

            return area;
        }
    }
}