interface Runnable
{
    void run();
}

class Animal implements Runnable
{
    public void run()
    {
        System.out.println("Animal.run()");
    }
}

class Person implements Runnable
{
    public void run()
    {
        System.out.println("Person.run()");
    }
}

class Other
{
    public void run()
    {
        System.out.println("A");
    }
}

public class Main
{
    static void runARunnable(Runnable r)
    {
        r.run();
    }

    public static void main(String[] args)
    {
        Person p = new Person();
        Animal a = new Animal();
        Other  o = new Other();
        runARunnable(p);
        runARunnable(a);

//      Syntax Error
//      runARunnable(o);
    }
}