很简单的题目，主要是要熟悉栈的原理，先进后出 
# -*- coding:utf-8 -*-
class Solution:
    def __init__(self) -> None:
        self.stack = []
        pass
    def push(self, node):
        # write code here
        self.stack.append(node)
    def pop(self):
        # write code here
        p = self.top()
        self.stack.__delitem__(len(self.stack) - 1)
        return p
    def top(self):
        # write code here
        return self.stack[-1]
    def min(self):
        # write code here
        return min(self.stack)