a-a a-b aaa aab aag aao aar aas ab- aba abb abg abo abr abs ag- aga agb agg ago agr ags aoa aob aog aoo aor aos ar- ara arb arg aro arr ars as- asa asb asg aso asr ass baa bab bag bao bar bas bba bbb bbg bbo bbr bbs bga bgb bgg bgo bgr bgs boa bob bog boo bor bos bra brb brg bro brr brs bsa bsb bsg bso bsr bss gaa gab gag gao gar gas gba gbg gbo gbr gbs gga ggb ggg ggo ggr ggs goa gob gog goo gor gos gra grb grg gro grr grs gsa gsb gsg gso gsr gss oaa oab oag oao oar oas ob- oba obb obg obo obr obs oga ogg ogo ogs oo- ooa oob oog ooo oor oos or- ora orb org oro orr ors os- osa osb osg oso osr oss ra- raa rab rag rao rar ras rba rbb rbg rbo rbr rbs rga rgb rgg rgo rgr rgs roa rob rog roo ror ros rra rrb rrg rrr rrs rsa rsb rsg rso rsr rss saa sab sag sao sar sas sba sbb sbg sbo sbr sbs sga sgb sgg sgo sgr sgs soa sob sog soo sor sos sr- sra srb srg sro srr srs ss- ssa ssb ssg sso ssr sss