from RA_stack import RA_stack

class highwater_RA_stack(RA_stack):
    """Additional attribute: max_height"""
    
    def highwater(self):
        return self.max_height

    def __init__(self):
        RA_stack.__init__(self)
        self.max_height = 0

    def push(self, item):
        RA_stack.push(self, item)
        if self.height() > self.max_height:
            self.max_height = self.height()