// Esta é uma cópia de algs4/ResizingArrayStack.java
// de Sedgewick e Wayne
// sem os comentários

import java.util.Iterator;
import java.util.NoSuchElementException;

public class ResizingArrayStack<Item> implements Iterable<Item> {

    private Item[] a; 
    private int N; 

    public ResizingArrayStack() {
        a = (Item[]) new Object[2];
    }

    public boolean isEmpty() {
        return N == 0;
    }

    public int size() {
        return N;
    }

    private void resize(int capacity) {
        assert capacity >= N;
        Item[] temp = (Item[]) new Object[capacity];
        for (int i = 0; i < N; i++) {
            temp[i] = a[i];
        }
        a = temp;
    }

    public void push(Item item) {
        if (N == a.length) resize(2*a.length);
        a[N++] = item;
    }

    public Item pop() {
        if (isEmpty()) throw new NoSuchElementException("Stack underflow");
        Item item = a[N-1];
        a[N-1] = null;
        N--;
        if (N > 0 && N == a.length/4) resize(a.length/2);
        return item;
    }

    public Item peek() {
        if (isEmpty()) throw new NoSuchElementException("Stack underflow");
        return a[N-1];
    }

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

    private class ReverseArrayIterator implements Iterator<Item> {
        private int i;
        public ReverseArrayIterator() {
            i = N;
        }
        public boolean hasNext() {
            return i > 0;
        }
        public void remove() {
            throw new UnsupportedOperationException();
        }
        public Item next() {
            if (!hasNext()) throw new NoSuchElementException();
            return a[--i];
        }
    }

    public static void main(String[] args) {
        ResizingArrayStack<String> s = new ResizingArrayStack<String>();
        while (!StdIn.isEmpty()) {
            String item = StdIn.readString();
            if (!item.equals("-")) s.push(item);
            else if (!s.isEmpty()) StdOut.print(s.pop() + " ");
        }
        StdOut.println("(" + s.size() + " left on stack)");
    }
}