a-a a-b a-c aaa aab aac aag aak aao ab- aba abb abc abg abk abo ac- aca acb acc acg ack aco ag- aga agb agc agg agk ago aka akb akc akg akk ako aoa aob aoc aog aok aoo baa bab bac bag bak bao bba bbb bbc bbg bbk bbo bca bcb bcc bcg bck bco bga bgb bgc bgg bgk bgo bka bkb bkc bkg bkk bko boa bob boc bog bok boo c-- caa cab cac cag cak cao cba cbb cbc cbg cbk cbo cca ccb ccc ccg cck cco cga cgb cgc cgg cgo cka ckb ckc cko co- coa cob coc cog cok coo gaa gab gac gag gak gao gba gbc gbg gbk gbo gca gcb gcc gcg gck gco gga ggb ggc ggg ggo gka gkb gko goa gob goc gog gok goo ka- kaa kab kac kag kak kao kba kbb kbc kbk kbo kca kcb kcc kcg kck kga kgb kgc kgo kkb kkc kkk koa kob koc kog kok koo oaa oab oac oag oak oao ob- oba obb obc obg obk obo oc- oca ocb occ ocg ock oco oga ogc ogg ogo oka okb okc okg okk oko oo- ooa oob ooc oog ook ooo