def spacegroup2poly(spacegroup):
    """
    Return the size of polygon appropiated to represent a given
    crystal system

    :param spacegroup:
    :return:
    """
    if spacegroup <= 2:
        return 3
    elif spacegroup <= 15:
        return 5
    elif spacegroup <= 74:
        return 7
    elif spacegroup <= 142:
        return 9
    elif spacegroup <= 167:
        return 8
    elif spacegroup <= 194:
        return 6
    else:
        return 4
