a-a a-b aaa aab aaf aag aao aar aas ab- aba abb abf abg abo abr abs af- afa afb aff afg afo afr afs ag- aga agb agf agg ago agr ags aoa aob aof aog aoo aor aos ar- ara arb arf arg aro arr ars as- asa asb asf asg aso asr ass baa bab baf bag bao bar bas bba bbb bbf bbg bbo bbr bbs bfa bfb bff bfg bfo bfr bfs bga bgb bgf bgg bgo bgr bgs boa bob bof bog boo bor bos bra brb brf brg bro brr brs bsa bsb bsf bsg bso bsr bss faa fab faf fag fao far fas fba fbb fbf fbg fbo fbr fbs ffa fff ffg ffo ffr ffs fga fgb fgf fgg fgr fgs foa fob fof fog foo for fos fra frb frf frg fro frr frs fsa fsb fsf fsg fso fsr fss gaa gab gaf gag gao gar gas gba gbf gbg gbo gbr gbs gfa gfb gff gfo gfr gfs gga ggb ggg ggo ggr ggs goa gob gof gog goo gor gos gra grb grf grg gro grr grs gsa gsb gsf gsg gso gsr gss oaa oab oaf oag oao oar oas ob- oba obb obf obg obo obr obs of- ofa ofb off ofg ofo ofr ofs oga ogf ogg ogo ogs oo- ooa oob oof oog ooo oor oos or- ora orb orf org oro orr ors os- osa osb osf osg oso osr oss ra- raa rab raf rag rao rar ras rba rbb rbf rbg rbo rbr rbs rfa rfb rff rfg rfo rfr rfs rga rgb rgf rgg rgo rgr rgs roa rob rof rog roo ror ros rra rrb rrf rrg rrr rrs rsa rsb rsf rsg rso rsr rss saa sab saf sag sao sar sas sba sbb sbf sbg sbo sbr sbs sfa sfb sff sfg sfo sfr sfs sga sgb sgf sgg sgo sgr sgs soa sob sof sog soo sor sos sr- sra srb srf srg sro srr srs ss- ssa ssb ssf ssg sso ssr sss