eHazi q/88999

class Node:
    def __init__(self, value, next = None):
        self.value = value
        self.next = next

class Stack:
    def __init__(self):
        self.top = None

    def pop(self):
        if self.top == None:
            return
        self.top = self.top.next

    def push(self, value):
        node = Node(value, self.top)
        self.top = node

class Queue:
    def __init__(self):
        self.top = None
        self.bottom = None

    def pop(self):
        if self.top == None:
            pass
        else:
            self.top = self.top.next

    def push(self, value):
        node = Node(value, None)
        if self.bottom == None:
            self.bottom = self.top = node
        else:
            self.bottom.next = node
            self.bottom = node