def angle_classifier(a: int) -> str:
    """Classify the angle.

    An acute angle is one smaller than 90 degrees.
    A right angle is one that is exactly 90 degrees.    
    An obtuse angle is one greater than 90 degrees
    (but smaller than 180 degrees).

    """
    if a > 90 and a < 180:
        return "obtuse"
    elif a < 90 and a > 0:
        return "acute"
    return "right"