a-a a-b aaa aab aag aao aar aas aax ab- aba abb abg abo abr abs abx ag- aga agb agg ago agr ags agx aoa aob aog aoo aor aos aox ar- ara arb arg aro arr ars arx as- asa asb asg aso asr ass asx ax- axa axo axr axs axx baa bab bag bao bar bas bax bba bbb bbg bbo bbr bbs bbx bga bgb bgg bgo bgr bgs bgx boa bob bog boo bor bos box bra brb brg bro brr brs brx bsa bsb bsg bso bsr bss bsx bxb bxo bxx gaa gab gag gao gar gas gba gbg gbo gbr gbs gbx gga ggb ggg ggo ggr ggs goa gob gog goo gor gos gox gra grb grg gro grr grs grx gsa gsb gsg gso gsr gss gsx gxa gxs oaa oab oag oao oar oas oax ob- oba obb obg obo obr obs obx oga ogg ogo ogs ogx oo- ooa oob oog ooo oor oos oox or- ora orb org oro orr ors orx os- osa osb osg oso osr oss osx ox- oxa oxb oxo oxx ra- raa rab rag rao rar ras rax rba rbb rbg rbo rbr rbs rbx rga rgb rgg rgo rgr rgs rgx roa rob rog roo ror ros rox rra rrb rrg rrr rrs rsa rsb rsg rso rsr rss rsx rxr rxs saa sab sag sao sar sas sax sba sbb sbg sbo sbr sbs sbx sga sgb sgg sgo sgr sgs sgx soa sob sog soo sor sos sox sr- sra srb srg sro srr srs srx ss- ssa ssb ssg sso ssr sss ssx sxs xaa xag xar xas xbr xbx xoa xog xoo xor xos xox xrx xsa xsb xss xxo xxx