public class MyStack {
    protected Object[] items;
    protected int n;

    public MyStack() {
	items = new Object[1000];
	n = 0;
    }
    public void push(Object item) {
	items[n++] = item;
    }
    public Object pop() {
	return items[--n];
    }
    public boolean empty() {
	return n == 0;
    }
}