class LinkedQueue :
    class _Node :

        def __init__(self, element, next):
            self._element = element
            self._next = next

        def get_elements(self):
            return self._element

        def set_elements(self, num):
            self._element = num

    def __init__(self) :
        self._head = None
        self._tail = None
        self._size = 0

    def display(self):
        tmp = self._head
        while tmp != None :
            print(tmp.get_elements())
            tmp = tmp._next

    def __len__(self) :
        return self._size

    def is_empty(self) :
        return self._size == 0

    def first(self) :
        if self.is_empty() :
            raise Empty('Queue is empty')
        return self._head._element

    def dequeue(self) :
        if self.is_empty():
            raise Empty('Queue is empty')
        answer = self._head._element
        self._head = self._head._next
        self._size -= 1
        if self.is_empty() :
            self._tail = None
        return answer

    def enqueue(self, e) :
        newest = self._Node(e,None)
        if self.is_empty() :
            self._head = newest
        else :
            self._tail._next = newest
        self._tail = newest
        self._size += 1

class Empty(Exception) :
    pass

def menu():
    queue = LinkedQueue()
    while True:
        print('n - to add a number')
        print('q - to quit')
        selection = input('Enter your selection: ')
        if selection == 'n':
            number = int(input("Enter a number: "))
            queue.enqueue(number)
        elif selection == 'q':
            break
    for item in queue.display():
        n = item

    counter = 0
    for i in range(len(queue)):
        counter += 1
        print('Entry # ', counter, '=', n)