class Stack:

    def __init__(self):
        self.stack = []

    def isEmpty(self):
        return self.stack == []

    def push(self, item):
        self.stack.append(item)

    def pop(self):
        if (self.isEmpty()):
            return None

        return self.stack.pop()

    def peek(self):
        if (self.isEmpty()):
            return None

        return self.stack[len(self.stack) - 1]


s = Stack()
print(s.isEmpty())
s.push(1)
s.push('two')
print(s.peek())
s.push(True)
print(s.isEmpty())
print(s.pop())
print(s.pop())
print(s.pop())
print(s.isEmpty())
print(s.pop())

class Stack:

    def __init__(self):
        self.stack = []

    def isEmpty(self):
        return self.stack == []

    def push(self, item):
        self.stack.append(item)

    def pop(self):
        if (self.isEmpty()):
            return None

        return self.stack.pop()

    def peek(self):
        if (self.isEmpty()):
            return None

        return self.stack[len(self.stack) - 1]


s = Stack()
print(s.isEmpty())
s.push(1)
s.push('two')
print(s.peek())
s.push(True)
print(s.isEmpty())
print(s.pop())
print(s.pop())
print(s.pop())
print(s.isEmpty())
print(s.pop())
