using System;

namespace AbstractClasses

{

    public class Program

    {

        public static void Main(string[] args)

        {

            Dog dog = new Dog();

            Console.WriteLine(dog.Describe());

        }

    }

abstract class FourLeggedAnimal

{

    public virtual string Describe()

    {

        return "This animal has four legs.";

    }

}

​

​

class Dog : FourLeggedAnimal

{

    public override string Describe()

    {

        string result = base.Describe();

        result += " In fact, it's a dog!";

        return result;

    }

​

}

}