a-a a-b a-c aaa aab aac aak aam aao ab- aba abb abc abk abm abo ac- aca acb acc ack acm aco aka akb akc akk akm ako ama amb amc amk amm amo aoa aob aoc aok aom aoo baa bab bac bak bam bao bba bbb bbc bbk bbm bbo bca bcb bcc bck bcm bco bka bkb bkc bkk bkm bko bma bmb bmc bmk bmm bmo boa bob boc bok bom boo c-- caa cab cac cak cam cao cba cbb cbc cbk cbm cbo cca ccb ccc cck ccm cco cka ckb ckc ckm cko cma cmb cmc cmk cmm cmo co- coa cob coc cok com coo ka- kaa kab kac kak kam kao kba kbb kbc kbk kbm kbo kca kcb kcc kck kcm kkb kkc kkk kkm kma kmb kmc kmk kmm kmo koa kob koc kok kom koo m-o maa mab mac mak mam mao mba mbb mbc mbk mbm mbo mc- mca mcb mcc mck mcm mco mka mkb mkc mkk mkm mko mma mmb mmc mmk mmm mmo moa mob moc mok mom moo oaa oab oac oak oam oao ob- oba obb obc obk obm obo oc- oca ocb occ ock ocm oco oka okb okc okk oko om- oma omb omc omm omo oo- ooa oob ooc ook oom ooo