class Node:
  def __init__(self):
    self.data = ""
    self.link = 0

class Stack:
  def __init__(self):
    self.top = 0

def add(stack, data):
  n = Node()
  n.data = data
  n.link = stack.top
  stack.top = n

def hasMore(stack):
  return stack.top != 0

def remove(stack):
  n = stack.top
  stack.top = n.link
  return n.data

s = Stack()
add(s, "AA")
add(s, "BB")
add(s, "CC")
while hasMore(s):
  print remove(s)