class stack():
	def __init__(self):
		self.el = []

	def empty (self):
		return len(self.el) == 0

	def push(self, x):
		self.el.append(x)
	
	def pop(self):
		if not self.empty():
			return self.el.pop()

	def look(self):
		if not self.empty():
			return self.el[len(self.el)-1]

	def show(self):
		print(self.el)


st = stack()
s = input('enter op:')
while s != 'exit':
	op = s.split()
	if len(op) == 1:
		if s == 'show':
			st.show()
		if s == 'look':
			if st.empty():
				print('stack is empty')
			else:
				print(st.look())
		if s == 'pop':
			if st.empty():
				print('stack is empty')
			else:
				print(st.pop())
	else: # push k
		st.push(int(op[1]))
	s = input('enter op:')
	
print('Thanks')