This function sets up a command-line option parser and then calls
    to do all of the real work.

def main(argv):
    """This function sets up a command-line option parser and then calls
    to do all of the real work.
    """
    import argparse
    import codecs
    # have to be ready to deal with utf-8 names
    out = codecs.getwriter('utf-8')(sys.stdout)
    description = '''Takes a series of at least 2 OTT ids and reports the OTT of their least inclusive taxonomic ancestor and that taxon's ancestors.'''
    parser = argparse.ArgumentParser(prog='ot-taxo-mrca-to-root', description=description)
    parser.add_argument('ids', nargs='+', type=int, help='OTT IDs')
    args = parser.parse_args(argv)
    id_list = args.ids
    last_id = id_list.pop()
    anc_list = get_taxonomic_ancestor_ids(last_id)
    common_anc = set(anc_list)
    for curr_id in id_list:
        curr_anc_set = set(get_taxonomic_ancestor_ids(curr_id))
        common_anc &= curr_anc_set
        if not common_anc:
            break
    for anc_id in anc_list:
        if anc_id in common_anc:
            out.write('{}\n'.format(anc_id))