import std.stdio;

interface Animal {
    void sound();
}

class Dog : Animal {
    override public void sound() {
        for (int i = 0; i <=3; ++i) write("hau");
        write("\n");
    }
}

class Cat : Animal {
    override public void sound() {
        for (int i = 0; i <= 5; ++i) write("miau");
        write("\n");
    }
}

void main() {
    Animal[] animals;

    animals ~= new Cat;
    animals ~= new Dog;

    foreach (animal; animals) {
        animal.sound();
    }
}