游乐园的过山车每次限坐4人，用循环队列管理排队，容量MAX=5，约定空一格判满。执行以下代码后，判断循环队列是否已满，rear的值是多少？

MAX = 5
queue = [None] * MAX
front = 0
rear = 0
def enqueue(x):
  global rear, queue
  queue[rear] = x
  rear = (rear + 1) % MAX

def dequeue():
  global front
  front = (front + 1) % MAX

if __name__ == "__main__":
  enqueue(1)
  enqueue(2)
  enqueue(3)
  enqueue(4)

  dequeue()
  dequeue()

  enqueue(5)
  enqueue(6)