a-a a-b a-c a-t aaa aab aac aaf aao aar aat ab- aba abb abc abf abo abr abt ac- aca acb acc acf aco acr act af- afa afb afc aff afo afr aft aoa aob aoc aof aoo aor aot ar- ara arb arc arf aro arr art at- ata atb atc atf ato atr att baa bab bac baf bao bar bat bba bbb bbc bbf bbo bbr bbt bca bcb bcc bcf bco bcr bct bfa bfb bfc bff bfo bfr bft boa bob boc bof boo bor bot bra brb brf bro brr brt bta btb btc btf bto btr btt c-- caa cab cac caf cao car cat cba cbb cbc cbf cbo cbr cbt cca ccb ccc ccf cco ccr cct cfa cfb cfc cff cfo cfr cft co- coa cob coc cof coo cor cot cra crb crc crf cro crr crt cta ctb ctc ctf cto ctr ctt faa fab fac faf fao far fat fba fbb fbc fbf fbo fbr fbt fca fcb fcc fcf fco fcr fct ffa ffc fff ffo ffr fft foa fob foc fof foo for fot fra frb frc frf fro frr frt fta ftb ftc ftf fto ftr ftt oaa oab oac oaf oao oar oat ob- oba obb obc obf obo obr obt oc- oca ocb occ ocf oco ocr oct of- ofa ofb ofc off ofo ofr oft oo- ooa oob ooc oof ooo oor oot or- ora orb orc orf oro orr ort ot- ota otb otc otf oto otr ott ra- raa rab rac raf rao rar rat rba rbb rbc rbf rbo rbr rbt rca rcb rcc rcf rco rcr rct rfa rfb rfc rff rfo rfr rft roa rob roc rof roo ror rot rra rrb rrc rrf rrr rrt rta rtb rtc rtf rto rtr rtt taa tab tac taf tao tar tat tba tbb tbc tbf tbo tbr tbt tca tcb tcc tcf tco tcr tct tfa tfb tfc tff tfo tfr tft to- toa tob toc tof too tor tot tra trb trc trf tro trr trt tta ttb ttc ttf tto ttr ttt