a-a a-c aaa aac aaf aah aao ac- aca acc acf ach aco af- afa afc aff afh afo aha ahc ahf ahh aho aoa aoc aof aoh aoo c-- caa cac caf cah cao cca ccc ccf cch cco cfa cfc cff cfh cfo ch- cha chc chf chh cho co- coa coc cof coh coo faa fac faf fah fao fca fcc fcf fco ffa ffc fff ffh ffo fha fhc fhf fhh fho foa foc fof foh foo haa hac haf hah hao hca hcc hcf hch hco hfa hfc hff hfh hfo hha hhc hhf hhh hho hoa hoc hof hoh hoo oaa oac oaf oah oao oc- oca occ ocf och oco of- ofa ofc off ofo oha ohc ohf ohh oho oo- ooa ooc oof ooh ooo