class Interval:
    def __init__(self, start, end):
        self.start = start
        self.end = end
        self.closed = True  # by default, the interval is closed
    # set the flag for closed/open

    def set_closed(self, closed):
        self.closed = closed

    def __str__(self):
        return "[" + str(self.start) + ", " + str(self.end) + "]" \
            if self.closed else \
                "(" + str(self.start) + ", " + str(self.end) + ")"