Simple Deque

deque = []

while True:
  command = input()
  if command == 'exit':
    print('bye')
    break
  elif command == 'size':
    print(len(deque))
  elif command == 'pop_front':
    print(deque.pop(0))
  elif command == 'front':
    print(deque[0])
  elif command == 'pop_back':
    print(deque.pop())
  elif command == 'back':
    print(deque[-1])
  elif command == 'clear':
    deque.clear()
    print('ok')
  else:
    cmd, n = command.split()
    if cmd == 'push_back':
      deque.append(n)
    else:
      deque.insert(0, n)
    print('ok')