a-a a-b a-c a-t aaa aab aac aaf aak aao aar aat ab- aba abb abc abf abk abo abr abt ac- aca acb acc acf ack aco acr act af- afa afb afc aff afk afo afr aft aka akb akc akk ako akr aoa aob aoc aof aok aoo aor aot ar- ara arb arc arf ark aro arr art at- ata atb atc atf ato atr att baa bab bac baf bak bao bar bat bba bbb bbc bbf bbk bbo bbr bbt bca bcb bcc bcf bck bco bcr bct bfa bfb bfc bff bfo bfr bft bka bkb bkc bkf bkk bko bkr bkt boa bob boc bof bok boo bor bot bra brb brf brk bro brr brt bta btb btc btf btk bto btr btt c-- caa cab cac caf cak cao car cat cba cbb cbc cbf cbk cbo cbr cbt cca ccb ccc ccf cck cco ccr cct cfa cfb cfc cff cfk cfo cfr cft cka ckb ckc cko ckt co- coa cob coc cof cok coo cor cot cra crb crc crf crk cro crr crt cta ctb ctc ctf ctk cto ctr ctt faa fab fac faf fak fao far fat fba fbb fbc fbf fbk fbo fbr fbt fca fcb fcc fcf fck fco fcr fct ffa ffc fff ffk ffo ffr fft fka fkb fkc fkf fkk fkt foa fob foc fof fok foo for fot fra frb frc frf frk fro frr frt fta ftb ftc ftf ftk fto ftr ftt k-t ka- kaa kab kac kaf kak kao kar kat kba kbb kbc kbf kbk kbo kbr kca kcb kcc kck kcr kct kfa kfc kff kfo kkb kkc kkk kkr kkt koa kob koc kof kok koo kor kot kra krc krf krk kro krr krt kta ktb ktc ktf ktk kto ktr ktt oaa oab oac oaf oak oao oar oat ob- oba obb obc obf obk obo obr obt oc- oca ocb occ ocf ock oco ocr oct of- ofa ofb ofc off ofo ofr oft oka okb okc okk oko okr oo- ooa oob ooc oof ook ooo oor oot or- ora orb orc orf ork oro orr ort ot- ota otb otc otf otk oto otr ott ra- raa rab rac raf rak rao rar rat rba rbb rbc rbf rbk rbo rbr rbt rca rcb rcc rcf rco rcr rct rfa rfb rfc rff rfk rfo rfr rft rkb rkc rkf rkk rko rkt roa rob roc rof rok roo ror rot rra rrb rrc rrf rrk rrr rrt rta rtb rtc rtf rtk rto rtr rtt taa tab tac taf tak tao tar tat tba tbb tbc tbf tbk tbo tbr tbt tca tcb tcc tcf tck tco tcr tct tfa tfb tfc tff tfk tfo tfr tft tka tkb tkc tkk tko tkr tkt to- toa tob toc tof tok too tor tot tra trb trc trf trk tro trr trt tta ttb ttc ttf ttk tto ttr ttt