'''
Implement a stack. You can use any data structure inside a stack except stack itself to implement it.

Example
push(1)
pop()
push(2)
top()  // return 2
pop()
isEmpty() // return true
push(3)
isEmpty() // return false
'''
class Stack:
    """
    @param: x: An integer
    @return: nothing
    """
    def push(self, x):
        # write your code here

    """
    @return: nothing
    """
    def pop(self):
        # write your code here

    """
    @return: An integer
    """
    def top(self):
        # write your code here

    """
    @return: True if the stack is empty
    """
    def isEmpty(self):
        # write your code here
