class MicrowaveBase:
    def __init__(self):
        self.time = "00:00"

    def set_time(self, time: str):
        self.time = time

    def add_time(self, time: str):
        minute, second = self.time.split(":")
        minute = int(minute)
        second = int(second)
        number_to_add = int(time[0:-1])
        unit_to_add = time[-1:]
        if unit_to_add == "s":
            second += number_to_add
            while second >= 60:
                minute += 1
                second = second - 60
        else:
            minute += number_to_add
        if minute > 90:
            self.time = "90:00"
        else:
            self.time = "{}:{}".format(str(minute).rjust(2, "0"), str(second).rjust(2, "0"))

    def del_time(self, time: str):
        minute, second = self.time.split(":")
        minute = int(minute)
        second = int(second)
        number_to_add = int(time[0:-1])
        unit_to_add = time[-1:]
        if unit_to_add == "s":
            second -= number_to_add
            while second <= 0:
                minute -= 1
                second *= -1
        else:
            minute -= number_to_add
        if minute < 0:
            self.time = "00:00"
        else:
            self.time = "{}:{}".format(str(minute).rjust(2, "0"), str(second).rjust(2, "0"))



class Microwave1(MicrowaveBase):
    def show_time(self) -> str:
        print("_"+self.time[1:])
        return "_"+self.time[1:]


class Microwave2(MicrowaveBase):
    def show_time(self):
        print(self.time[0:-1] + "_")
        return self.time[0:-1] + "_"


class Microwave3(MicrowaveBase):
    def show_time(self):
        print(self.time)
        return self.time


class RemoteControl:
    def __init__(self, microwave: MicrowaveBase):
        self.microwave = microwave

    def set_time(self, time: str):
        self.microwave.set_time(time)

    def add_time(self, time: str):
        self.microwave.add_time(time)

    def del_time(self, time: str):
        self.microwave.del_time(time)

    def show_time(self):
        return self.microwave.show_time()


if __name__ == '__main__':
    # These "asserts" using only for self-checking and not necessary for auto-testing

    microwave_1 = Microwave1()
    microwave_2 = Microwave2()
    microwave_3 = Microwave3()

    remote_control_1 = RemoteControl(microwave_1)
    remote_control_1.set_time("01:00")

    remote_control_2 = RemoteControl(microwave_2)
    remote_control_2.add_time("90s")

    remote_control_3 = RemoteControl(microwave_3)
    remote_control_3.del_time("300s")
    remote_control_3.add_time("100s")

    assert remote_control_1.show_time() == "_1:00"
    assert remote_control_2.show_time() == "01:3_"
    assert remote_control_3.show_time() == "01:40"
    print("Coding complete? Let's try tests!")