using System;

​

class Program

{

    static void Main(string[] args)

    {

        Shape shape = new Circle();

        Console.WriteLine(shape.GetShape());

        shape = new Triangle();

        Console.WriteLine(shape.GetShape());

    }

}

​

public abstract class Shape

{

    public abstract string GetShape();

}

​

public class Triangle : Shape

{

    public override string GetShape()

    {

        return "Triangle";

    }

}

​

public class Circle : Triangle

{

    public override string GetShape()

    {

        return "Circle";

    }

}