class Tester {

    public static void main(String[] args) {
	List numbers = new List();
	numbers.putAtFront(4);
	numbers.putAtFront(3);
	numbers.putAtFront(9);
	numbers.putAtFront(12);
	System.out.println(numbers);
	System.out.println(numbers.search(6));
	System.out.println(numbers.search(9));
	System.out.println(numbers.search(4));
	System.out.println(numbers.search(0));
	
    }

}