a-a a-b a-c aaa aab aac aam aao ab- aba abb abc abm abo ac- aca acb acc acm aco ama amb amc amm amo aoa aob aoc aom aoo baa bab bac bam bao bba bbb bbc bbm bbo bca bcb bcc bcm bco bma bmb bmc bmm bmo boa bob boc bom boo c-- caa cab cac cam cao cba cbb cbc cbm cbo cca ccb ccc ccm cco cma cmb cmc cmm cmo co- coa cob coc com coo m-o maa mab mac mam mao mba mbb mbc mbm mbo mc- mca mcb mcc mcm mco mma mmb mmc mmm mmo moa mob moc mom moo oaa oab oac oam oao ob- oba obb obc obm obo oc- oca ocb occ ocm oco om- oma omb omc omm omo oo- ooa oob ooc oom ooo