a-a a-b a-t aaa aab aaf aak aao aar aas aat ab- aba abb abf abk abo abr abs abt af- afa afb aff afk afo afr afs aft aka akb akk ako akr aks aoa aob aof aok aoo aor aos aot ar- ara arb arf ark aro arr ars art as- asa asb asf ask aso asr ass ast at- ata atb atf ato atr ats att baa bab baf bak bao bar bas bat bba bbb bbf bbk bbo bbr bbs bbt bfa bfb bff bfo bfr bfs bft bka bkb bkf bkk bko bkr bks bkt boa bob bof bok boo bor bos bot bra brb brf brk bro brr brs brt bsa bsb bsf bsk bso bsr bss bst bta btb btf btk bto btr bts btt faa fab faf fak fao far fas fat fba fbb fbf fbk fbo fbr fbs fbt ffa fff ffk ffo ffr ffs fft fka fkb fkf fkk fkt foa fob fof fok foo for fos fot fra frb frf frk fro frr frs frt fsa fsb fsf fsk fso fsr fss fst fta ftb ftf ftk fto ftr fts ftt k-t ka- kaa kab kaf kak kao kar kas kat kba kbb kbf kbk kbo kbr kbs kfa kff kfo kfs kkb kkk kkr kks kkt koa kob kof kok koo kor kos kot kra krf krk kro krr krs krt ksa ksb ksf ksk kso ksr kss kst kta ktb ktf ktk kto ktr kts ktt oaa oab oaf oak oao oar oas oat ob- oba obb obf obk obo obr obs obt of- ofa ofb off ofo ofr ofs oft oka okb okk oko okr oks oo- ooa oob oof ook ooo oor oos oot or- ora orb orf ork oro orr ors ort os- osa osb osf osk oso osr oss ost ot- ota otb otf otk oto otr ots ott ra- raa rab raf rak rao rar ras rat rba rbb rbf rbk rbo rbr rbs rbt rfa rfb rff rfk rfo rfr rfs rft rkb rkf rkk rko rks rkt roa rob rof rok roo ror ros rot rra rrb rrf rrk rrr rrs rrt rsa rsb rsf rsk rso rsr rss rst rta rtb rtf rtk rto rtr rts rtt saa sab saf sak sao sar sas sat sba sbb sbf sbk sbo sbr sbs sbt sfa sfb sff sfk sfo sfr sfs sft sk- ska skb skf skk sko skr sks skt soa sob sof sok soo sor sos sot sr- sra srb srf srk sro srr srs srt ss- ssa ssb ssf ssk sso ssr sss sst sta stb stf stk sto str sts stt taa tab taf tak tao tar tas tat tba tbb tbf tbk tbo tbr tbs tbt tfa tfb tff tfk tfo tfr tfs tft tka tkb tkk tko tkr tks tkt to- toa tob tof tok too tor tos tot tra trb trf trk tro trr trs trt tsa tsb tsf tsk tso tsr tss tst tta ttb ttf ttk tto ttr tts ttt