a-a a-b aaa aab aag aak aao aas ab- aba abb abg abk abo abs ag- aga agb agg agk ago ags aka akb akg akk ako aks aoa aob aog aok aoo aos as- asa asb asg ask aso ass baa bab bag bak bao bas bba bbb bbg bbk bbo bbs bga bgb bgg bgk bgo bgs bka bkb bkg bkk bko bks boa bob bog bok boo bos bsa bsb bsg bsk bso bss gaa gab gag gak gao gas gba gbg gbk gbo gbs gga ggb ggg ggo ggs gka gkb gko gks goa gob gog gok goo gos gsa gsb gsg gsk gso gss ka- kaa kab kag kak kao kas kba kbb kbk kbo kbs kga kgb kgo kgs kkb kkk kks koa kob kog kok koo kos ksa ksb ksg ksk kso kss oaa oab oag oak oao oas ob- oba obb obg obk obo obs oga ogg ogo ogs oka okb okg okk oko oks oo- ooa oob oog ook ooo oos os- osa osb osg osk oso oss saa sab sag sak sao sas sba sbb sbg sbk sbo sbs sga sgb sgg sgk sgo sgs sk- ska skb skg skk sko sks soa sob sog sok soo sos ss- ssa ssb ssg ssk sso sss