# -*- coding:utf-8 -*-

 class Solution:

     def __init__(self):

         self.stack1=[]

         self.stack2=[]

     def push(self, node):

         # write code here

         self.stack1.append(node)

         if len(self.stack2)==0 or self.stack2[-1]>node:

             self.stack2.append(node)

         else:

             self.stack2.append(self.stack2[-1])

     def pop(self):

         if len(self.stack1)>0:

             self.stack2.pop()

             return self.stack1.pop()

         # write code here

     def top(self):

         # write code here

         if len(self.stack1)>0:

             return self.stack1[-1]

     def min(self):

         # write code here

         if len(self.stack2)>0:

             return self.stack2[-1]