abstract class Dyr{

    abstract void lagLyd();

}

class Hund extends Dyr{
    void lagLyd(){
        System.out.println("Voff!");
    }
}

class Katt extends Dyr{
    void lagLyd(){
        System.out.println("Mjau!");
    }


}

class TestDyr{
    public static void main(String[] args){
        Dyr hund1 = new Hund();
        Dyr katt1 = new Katt();

        hund1.lagLyd();
        katt1.lagLyd();
    }
}