a-a a-b a-t aaa aab aak aao aar aas aat ab- aba abb abk abo abr abs abt aka akb akk ako akr aks aoa aob aok aoo aor aos aot ar- ara arb ark aro arr ars art as- asa asb ask aso asr ass ast at- ata atb ato atr ats att baa bab bak bao bar bas bat bba bbb bbk bbo bbr bbs bbt bka bkb bkk bko bkr bks bkt boa bob bok boo bor bos bot bra brb brk bro brr brs brt bsa bsb bsk bso bsr bss bst bta btb btk bto btr bts btt k-t ka- kaa kab kak kao kar kas kat kba kbb kbk kbo kbr kbs kkb kkk kkr kks kkt koa kob kok koo kor kos kot kra krk kro krr krs krt ksa ksb ksk kso ksr kss kst kta ktb ktk kto ktr kts ktt oaa oab oak oao oar oas oat ob- oba obb obk obo obr obs obt oka okb okk oko okr oks oo- ooa oob ook ooo oor oos oot or- ora orb ork oro orr ors ort os- osa osb osk oso osr oss ost ot- ota otb otk oto otr ots ott ra- raa rab rak rao rar ras rat rba rbb rbk rbo rbr rbs rbt rkb rkk rko rks rkt roa rob rok roo ror ros rot rra rrb rrk rrr rrs rrt rsa rsb rsk rso rsr rss rst rta rtb rtk rto rtr rts rtt saa sab sak sao sar sas sat sba sbb sbk sbo sbr sbs sbt sk- ska skb skk sko skr sks skt soa sob sok soo sor sos sot sr- sra srb srk sro srr srs srt ss- ssa ssb ssk sso ssr sss sst sta stb stk sto str sts stt taa tab tak tao tar tas tat tba tbb tbk tbo tbr tbs tbt tka tkb tkk tko tkr tks tkt to- toa tob tok too tor tos tot tra trb trk tro trr trs trt tsa tsb tsk tso tsr tss tst tta ttb ttk tto ttr tts ttt