a-a a-b aaa aab aag aak aao aar aas ab- aba abb abg abk abo abr abs ag- aga agb agg agk ago agr ags aka akb akg akk ako akr aks aoa aob aog aok aoo aor aos ar- ara arb arg ark aro arr ars as- asa asb asg ask aso asr ass baa bab bag bak bao bar bas bba bbb bbg bbk bbo bbr bbs bga bgb bgg bgk bgo bgr bgs bka bkb bkg bkk bko bkr bks boa bob bog bok boo bor bos bra brb brg brk bro brr brs bsa bsb bsg bsk bso bsr bss gaa gab gag gak gao gar gas gba gbg gbk gbo gbr gbs gga ggb ggg ggo ggr ggs gka gkb gko gks goa gob gog gok goo gor gos gra grb grg grk gro grr grs gsa gsb gsg gsk gso gsr gss ka- kaa kab kag kak kao kar kas kba kbb kbk kbo kbr kbs kga kgb kgo kgs kkb kkk kkr kks koa kob kog kok koo kor kos kra krg krk kro krr krs ksa ksb ksg ksk kso ksr kss oaa oab oag oak oao oar oas ob- oba obb obg obk obo obr obs oga ogg ogo ogs oka okb okg okk oko okr oks oo- ooa oob oog ook ooo oor oos or- ora orb org ork oro orr ors os- osa osb osg osk oso osr oss ra- raa rab rag rak rao rar ras rba rbb rbg rbk rbo rbr rbs rga rgb rgg rgk rgo rgr rgs rkb rkg rkk rko rks roa rob rog rok roo ror ros rra rrb rrg rrk rrr rrs rsa rsb rsg rsk rso rsr rss saa sab sag sak sao sar sas sba sbb sbg sbk sbo sbr sbs sga sgb sgg sgk sgo sgr sgs sk- ska skb skg skk sko skr sks soa sob sog sok soo sor sos sr- sra srb srg srk sro srr srs ss- ssa ssb ssg ssk sso ssr sss