a-a a-b a-c a-t aaa aab aac aan aar aat ab- aba abb abc abn abr abt ac- aca acb acc acn acr act an- ana anb anc ann anr ant ar- ara arb arc arn arr art at- ata atb atc atn atr att baa bab bac ban bar bat bba bbb bbc bbn bbr bbt bca bcb bcc bcn bcr bct bna bnb bnc bnn bnr bnt bra brb brn brr brt bta btb btc btn btr btt c-- caa cab cac can car cat cba cbb cbc cbn cbr cbt cca ccb ccc ccn ccr cct cn- cna cnb cnc cnn cnr cnt cra crb crc crn crr crt cta ctb ctc ctn ctr ctt naa nab nac nan nar nat nba nbb nbc nbn nbr nbt nca ncb ncc ncn ncr nct nna nnb nnc nnn nnt nra nrb nrc nrn nrr nrt nta ntb ntc ntn ntr ntt ra- raa rab rac ran rar rat rba rbb rbc rbn rbr rbt rca rcb rcc rcn rcr rct rna rnb rnc rnn rnr rnt rra rrb rrc rrn rrr rrt rta rtb rtc rtn rtr rtt taa tab tac tan tar tat tba tbb tbc tbn tbr tbt tca tcb tcc tcn tcr tct tna tnb tnc tnn tnr tnt tra trb trc trn trr trt tta ttb ttc ttn ttr ttt