import java.util.Iterator;

public class Stack<Item> implements Iterable<Item> {
    private Node first;
    private int N;

    private class Node {
        Item item;
        Node next;
    }

    public void push(Item item) {
        Node oldfirst = first;
        first = new Node();
        first.item = item;
        first.next = oldfirst;
        N++;
    }

    public Item pop() {
        Item item = first.item;
        first = first.next;
        N--;
        return item;
    }

    public Iterator<Item> iterator() {
        return new ReverseArrayIterator();
    }

    private class ReverseArrayIterator implements Iterator<Item> {
        private int i = N;

        @Override
        public boolean hasNext() {
            return i > 0;
        }

        @Override
        public Item next() {
            Node nextnode = first;
            for (int j = 0; j < N - i; j++)
                nextnode = nextnode.next;
            i--;
            return nextnode.item;
        }

        public void remove() {
        }
    }

    public static void main(String[] args) {
        Stack<Integer> s = new Stack<Integer>();
        s.push(1);
        s.push(2);
        s.push(3);
        for (int i : s)
            System.out.println(i);
    }
}