#後進先出:棧
class stack(object):
    def __init__(self):
        self.data =[]

    def push(self,item):
        self.data.append(item)

    def pop(self):
        return self.data.pop()

#先進先出:佇列

class Queue(object):
    def __init__(self):
        self.data=[]

    def push(self,item):
        self.data.insert(0,item)

    def pop(self):
        return self.data.pop()