a-a a-b aaa aab aak aam aao ab- aba abb abk abm abo aka akb akk akm ako ama amb amk amm amo aoa aob aok aom aoo baa bab bak bam bao bba bbb bbk bbm bbo bka bkb bkk bkm bko bma bmb bmk bmm bmo boa bob bok bom boo ka- kaa kab kak kam kao kba kbb kbk kbm kbo kkb kkk kkm kma kmb kmk kmm kmo koa kob kok kom koo m-o maa mab mak mam mao mba mbb mbk mbm mbo mka mkb mkk mkm mko mma mmb mmk mmm mmo moa mob mok mom moo oaa oab oak oam oao ob- oba obb obk obm obo oka okb okk oko om- oma omb omm omo oo- ooa oob ook oom ooo