from typing import Union


class AverageCounter:
    def __init__(self):
        self._elements_count = 0
        self._elements_sum = 0

    def add(self, number: int) -> None:
        self._elements_count += 1
        self._elements_sum += number

    def reset(self) -> None:
        self._elements_count = 0
        self._elements_sum = 0

    @property
    def average(self) -> Union[int, float]:
        if self._elements_count > 0:
            return self._elements_sum / self._elements_count


def main():
    average_counter = AverageCounter()

    average_counter.add(1)
    average_counter.add(2)
    average_counter.add(3)
    print(average_counter.average)

    average_counter.reset()
    print(average_counter.average)


if __name__ == "__main__":
    main()