def rotation_style(value: str) ->str:
    """
    Determine the rotation style.

    :param value: String representation of rotation style
    :return: Normalised rotation style
    """
    lower_value = value.lower()
    if lower_value in ('hour', 'hourly'):
        return 'h'
    elif lower_value in ('day', 'daily'):
        return 'd'
    elif lower_value in ('week', 'weekly'):
        return 'w'
    elif lower_value == 'size':
        return 'SIZE'
    else:
        raise ValueError('Rotation style must be hourly, daily, weekly or size'
            )
