def drusen(drusize: int) -> int:
    """
    DRSZWI: MAXIMUM DRUSEN W/I GRID

        0=None
        1=Quest
        2=<C0 (63)
        3=<C1 (125)
        4=<C2 (250)
        5=>=C2
        8=CG

    Returns:
        0, 1, 2, 88
    """
    drszwi = drusize
    if 0 <= drszwi <= 2:
        return 0
    elif drszwi == 3:
        return 1
    elif 4 <= drszwi <= 5:
        return 2
    elif drszwi == 8 or drszwi == 88:
        return 88
    else:
        raise KeyError('drarwi: %s' % drszwi)