class MinStack(object):

    def __init__(self):
        self.st=[] #stack
        self.min=None #min element

    def push(self, val):
        """
        :type val: int
        :rtype: None
        """
        if len(self.st)==0:
            self.st.append(val)
            self.min=val
        else:
            if val>=self.min:
                self.st.append(val)
            else:
                self.st.append(2*val-self.min)
                self.min=val

    def pop(self):
        """
        :rtype: None
        """
        x=self.st.pop() 
        if x<self.min:
            self.min=2*self.min-x

    def top(self):
        """
        :rtype: int
        """
        x=self.st[-1]
        if x>=self.min:
            return x
        return self.min
        

    def getMin(self):
        """
        :rtype: int
        """
        return self.min
        

minStack = MinStack()
minStack.push(-2)
minStack.push(0)
minStack.push(-3)
minStack.getMin() # return -3
minStack.pop()
minStack.top()    # return 0
minStack.getMin() # return -2



# Your MinStack object will be instantiated and called as such:
# obj = MinStack()
# obj.push(val)
# obj.pop()
# param_3 = obj.top()
# param_4 = obj.getMin()