class Node:
    def __init__(self, value):
        self.val = value
        self.next = None
class Stack:
    def __init__(self):
        self.head = None
    def push(self, el):
        if self.head == None:
            self.head = Node(el)
        else:
            tmp = Node(el)
            tmp.next = self.head
            self.head = tmp
    def pop(self):
        self.head = self.head.next

    def print(self):
        tmp = self.head
        while tmp is not None:
            print(tmp.val,end='\n')
            tmp = tmp.next