class Queue(object):
    def __init__(self):
        self.front = self.back = None

    def add(self, item):
        self.back = Node(item, self.back)
        if self.isEmpty():
            self.front = self.back

    def remove(self):
        pass
        # Your code here

    def isEmpty(self):
        return self.front == None

    def __len__(self):
        n = self.front
        count = 0
        while n != None:
            count += 1
            n = n.next
        return count
 
    def __contains__(self, value):
        pass
        # Your code here

class Node(object):
    def __init__(self, value, before):
        if before != None:
            before.next = self
        self.value = value
        self.next = None