class CannotFlyException extends Exception {}
interface Birdie {
    public abstract void fly() throws CannotFlyException;
}
interface Biped {
    public void walk();
}
abstract class NonFlyer {
    public void fly() { System.out.print("cannot fly "); } // LINE A
}
class Penguin extends NonFlyer implements Birdie, Biped { // LINE B
    public void walk() { System.out.print("walk "); }
}
class PenguinTest {
    public static void main(String []args) {
        Penguin pingu = new Penguin();
        pingu.walk();
        pingu.fly();
    }
}

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