using System;

​

public class Program

{

    public static void Main()

    {

        Dog dog = new Dog();

        dog.NumberOfLegs = 4;

        Bird bird = new Bird();

        bird.NumberOfLegs = 2;

    }

}

​

public interface Animal

{

    int NumberOfLegs { get; set; }

}

​

public class Dog : Animal

{

    public int NumberOfLegs {get;set;}

}

​

public class Bird : Animal

{

    public int NumberOfLegs { get; set; }

}