a-a a-b a-c aaa aab aac aah aao ab- aba abb abc abh abo ac- aca acb acc ach aco aha ahb ahc ahh aho aoa aob aoc aoh aoo baa bab bac bah bao bba bbb bbc bbh bbo bca bcb bcc bch bco bha bhb bhc bhh bho boa bob boc boh boo c-- caa cab cac cah cao cba cbb cbc cbh cbo cca ccb ccc cch cco ch- cha chb chc chh cho co- coa cob coc coh coo haa hab hac hah hao hba hbb hbc hbh hbo hca hcb hcc hch hco hha hhb hhc hhh hho hoa hob hoc hoh hoo oaa oab oac oah oao ob- oba obb obc obh obo oc- oca ocb occ och oco oha ohc ohh oho oo- ooa oob ooc ooh ooo