a-a a-b a-c a-t aaa aab aac aan aat ab- aba abb abc abn abt ac- aca acb acc acn act an- ana anb anc ann ant at- ata atb atc atn att baa bab bac ban bat bba bbb bbc bbn bbt bca bcb bcc bcn bct bna bnb bnc bnn bnt bta btb btc btn btt c-- caa cab cac can cat cba cbb cbc cbn cbt cca ccb ccc ccn cct cn- cna cnb cnc cnn cnt cta ctb ctc ctn ctt naa nab nac nan nat nba nbb nbc nbn nbt nca ncb ncc ncn nct nna nnb nnc nnn nnt nta ntb ntc ntn ntt taa tab tac tan tat tba tbb tbc tbn tbt tca tcb tcc tcn tct tna tnb tnc tnn tnt tta ttb ttc ttn ttt