def calculate_discount(initial: int, current: int) -> int:
    """
    Calculates the % difference between initial and current price.

    Note: when initial is 0 (that is, old price was lower than the new one -
    very unlikely in Steam), we assume that increase is (new price * 100)%.

    :param initial: initial price
    :param current: current price
    :return integer: representing the discount
    """

    if initial is None or current is None:
        return 0

    if current == 0:
        return -100

    difference = current - initial
    # Division by 0 is not allowed. 1, however, will not change the price.
    initial = 1 if initial == 0 else initial
    percent = (difference / initial) * 100

    return int(round(percent, 0))