text: """492. Implement Queue by Linked List"""
  class listNode(object):
      def __init__(self, val, next = None):
          self.val = val
          self.next = None
  
  class MyQueue:
      """
      @param: item: An integer
      @return: nothing
      """
      def __init__(self):
          self.first = None
          self.last = None
  
      def enqueue(self, item):
          # write your code here
          if self.first is None:
              self.first = listNode(item)
              self.last = self.first
          else:
              self.last.next = listNode(item)
              self.last = self.last.next
      """
      @return: An integer
      """
      def dequeue(self):
          # write your code here
          if self.first is None:
              return -1
          else:
              item = self.first.val
              self.first = self.first.next
              return item
  