Queue

queue = []

while True:
  cmd = input()
  if cmd == "exit":
    print("bye")
    break
  elif cmd == 'pop':
    print( queue.pop(0) )
  elif cmd == 'front':
    print( queue[0] )
  elif cmd == 'size':
    print( len(queue) )
  elif cmd == 'clear':
    queue.clear()
    print('ok')
  else:
    c, n = cmd.split()
    queue.append(n)
    print('ok')