a-a a-b a-c aaa aab aac aag aak aao aas ab- aba abb abc abg abk abo abs ac- aca acb acc acg ack aco acs ag- aga agb agc agg agk ago ags aka akb akc akg akk ako aks aoa aob aoc aog aok aoo aos as- asa asb asc asg ask aso ass baa bab bac bag bak bao bas bba bbb bbc bbg bbk bbo bbs bca bcb bcc bcg bck bco bcs bga bgb bgc bgg bgk bgo bgs bka bkb bkc bkg bkk bko bks boa bob boc bog bok boo bos bsa bsb bsc bsg bsk bso bss c-- caa cab cac cag cak cao cas cba cbb cbc cbg cbk cbo cbs cca ccb ccc ccg cck cco ccs cga cgb cgc cgg cgo cgs cka ckb ckc cko cks co- coa cob coc cog cok coo cos csa csb csc csg csk cso css gaa gab gac gag gak gao gas gba gbc gbg gbk gbo gbs gca gcb gcc gcg gck gco gcs gga ggb ggc ggg ggo ggs gka gkb gko gks goa gob goc gog gok goo gos gsa gsb gsc gsg gsk gso gss ka- kaa kab kac kag kak kao kas kba kbb kbc kbk kbo kbs kca kcb kcc kcg kck kcs kga kgb kgc kgo kgs kkb kkc kkk kks koa kob koc kog kok koo kos ksa ksb ksc ksg ksk kso kss oaa oab oac oag oak oao oas ob- oba obb obc obg obk obo obs oc- oca ocb occ ocg ock oco ocs oga ogc ogg ogo ogs oka okb okc okg okk oko oks oo- ooa oob ooc oog ook ooo oos os- osa osb osc osg osk oso oss saa sab sac sag sak sao sas sba sbb sbc sbg sbk sbo sbs sca scb scc scg sck sco scs sga sgb sgc sgg sgk sgo sgs sk- ska skb skc skg skk sko sks soa sob soc sog sok soo sos ss- ssa ssb ssc ssg ssk sso sss