a-a a-b a-c a-t aaa aab aac aao aar aat ab- aba abb abc abo abr abt ac- aca acb acc aco acr act aoa aob aoc aoo aor aot ar- ara arb arc aro arr art at- ata atb atc ato atr att baa bab bac bao bar bat bba bbb bbc bbo bbr bbt bca bcb bcc bco bcr bct boa bob boc boo bor bot bra brb bro brr brt bta btb btc bto btr btt c-- caa cab cac cao car cat cba cbb cbc cbo cbr cbt cca ccb ccc cco ccr cct co- coa cob coc coo cor cot cra crb crc cro crr crt cta ctb ctc cto ctr ctt oaa oab oac oao oar oat ob- oba obb obc obo obr obt oc- oca ocb occ oco ocr oct oo- ooa oob ooc ooo oor oot or- ora orb orc oro orr ort ot- ota otb otc oto otr ott ra- raa rab rac rao rar rat rba rbb rbc rbo rbr rbt rca rcb rcc rco rcr rct roa rob roc roo ror rot rra rrb rrc rrr rrt rta rtb rtc rto rtr rtt taa tab tac tao tar tat tba tbb tbc tbo tbr tbt tca tcb tcc tco tcr tct to- toa tob toc too tor tot tra trb trc tro trr trt tta ttb ttc tto ttr ttt