/*************************************************************************
 *  A generic stack, implemented using a singly-linked list.
 *  Each stack element is of type Item.
 *
 *  This version uses a static nested class Node (to save 8 bytes per
 *  Node), whereas the version in the textbook uses a non-static nested
 *  class (for simplicity).
 *
 *************************************************************************/
import java.util.Iterator;
import java.util.Scanner;
import java.util.NoSuchElementException;

public class Stack<Item> implements Iterable<Item> {
    private int N;                // size of the stack
    private Node<Item> first;     // top of stack

    // helper linked list class
    private static class Node<Item> {
        private Item item;
        private Node<Item> next;
    }

    public Stack() {
        first = null;
        N = 0;
    }

    /**
     * Is this stack empty?
     * @return true if this stack is empty; false otherwise
     */
    public boolean isEmpty() {
        return first == null;
    }

    /**
     * Returns the number of items in the stack.
     * @return the number of items in the stack
     */
    public int size() {
        return N;
    }

    /**
     * Adds the item to this stack.
     * @param item the item to add
     */
    public void push(Item item) {
        Node<Item> oldfirst = first;
        first = new Node<Item>();
        first.item = item;
        first.next = oldfirst;
        N++;
    }

    /**
     * Removes and returns the item most recently added to this stack.
     * @return the item most recently added
     * @throws java.util.NoSuchElementException if this stack is empty
     */
    public Item pop() {
        if (isEmpty()) throw new NoSuchElementException("Stack underflow");
        Item item = first.item;        // save item to return
        first = first.next;            // delete first node
        N--;
        return item;                   // return the saved item
    }


    /**
     * Returns (but does not remove) the item most recently added to this stack.
     * @return the item most recently added to this stack
     * @throws java.util.NoSuchElementException if this stack is empty
     */
    public Item peek() {
        if (isEmpty()) throw new NoSuchElementException("Stack underflow");
        return first.item;
    }

    /**
     * Returns a string representation of this stack.
     * @return the sequence of items in the stack in LIFO order, separated by spaces
     */
    public String toString() {
        StringBuilder s = new StringBuilder();
        for (Item item : this)
            s.append(item + " ");
        return s.toString();
    }
       

    /**
     * Returns an iterator to this stack that iterates through the items in LIFO order.
     * @return an iterator to this stack that iterates through the items in LIFO order.
     */
    public Iterator<Item> iterator() {
        return new ListIterator<Item>(first);
    }

    // an iterator, doesn't implement remove() since it's optional
    private class ListIterator<Item> implements Iterator<Item>
    {
        private Node<Item> current;

        public ListIterator(Node<Item> first)
	{
            current = first;
        }

	public boolean hasNext()  { return current != null;                     }
        public void remove()      { throw new UnsupportedOperationException();  }

        public Item next() {
            if (!hasNext()) throw new NoSuchElementException();
            Item item = current.item;
            current = current.next; 
            return item;
        }
    }


     /**
     * Unit tests the <tt>Stack</tt> data type.
     */
    public static void main(String [] args){
	Scanner sc  = new Scanner(System.in);
	Stack<String> s = new Stack<String>();
	while (sc.hasNext()){
	    String item = sc.next();
	    s.push(item);
	    System.out.println(s.size());
	}
	

    }
}