abstract class Animal {
    public abstract void makeSound();
}

interface Swimmable {
    void swim();
}

class Dog extends Animal implements Swimmable {
    @Override
    public void makeSound() {
        System.out.println("汪汪汪！");
    }

    @Override
    public void swim() {
        System.out.println("小狗在水里游泳！");
    }
}

class Cat extends Animal {
    @Override
    public void makeSound() {
        System.out.println("喵喵喵！");
    }
}