using System;

​

class Program {

  public static void Main (string[] args) {

    Dog animal1 = new Dog();

    Cat animal2 = new Cat();

    Duck animal3 = new Duck();

​

    animal1.sayHello();

    animal2.sayHello();

    animal3.sayHello();

  }

}

class Dog{

  public void sayHello(){

    Console.WriteLine("Bark");

  }

}

class Cat{

  public void sayHello(){

    Console.WriteLine("Meow");

  }

}

class Duck{

  public void sayHello(){

    Console.WriteLine("Quack");

  }

}

​