interface Animal
{
    void Speak();
}

interface Mammal : Animal
{
    void Walk();
}

class Dog : Mammal
{
    void Animal.Speak()
    {
        Console.WriteLine("Woof!");
    }

    void Mammal.Walk()
    {
        Console.WriteLine("The dog is walking.");
    }

    public void Eat()
    {
        Console.WriteLine("The dog is eating.");
    }
}

class Program
{
    static void Main(string[] args)
    {
        Dog d = new Dog();
        d.Eat();

        Animal a = d;
        a.Speak();

        Mammal m = d;
        m.Walk();
    }
}