a-a a-b a-c a-t aaa aab aac aan aas aat ab- aba abb abc abn abs abt ac- aca acb acc acn acs act an- ana anb anc ann ans ant as- asa asb asc asn ass ast at- ata atb atc atn ats att baa bab bac ban bas bat bba bbb bbc bbn bbs bbt bca bcb bcc bcn bcs bct bna bnb bnc bnn bns bnt bsa bsb bsc bsn bss bst bta btb btc btn bts btt c-- caa cab cac can cas cat cba cbb cbc cbn cbs cbt cca ccb ccc ccn ccs cct cn- cna cnb cnc cnn cns cnt csa csb csc csn css cst cta ctb ctc ctn cts ctt naa nab nac nan nas nat nba nbb nbc nbn nbs nbt nca ncb ncc ncn ncs nct nna nnb nnc nnn nns nnt nsa nsb nsc nsn nss nst nta ntb ntc ntn nts ntt saa sab sac san sas sat sba sbb sbc sbn sbs sbt sca scb scc scn scs sct sna snb snc snn sns snt ss- ssa ssb ssc ssn sss sst sta stb stc stn sts stt taa tab tac tan tas tat tba tbb tbc tbn tbs tbt tca tcb tcc tcn tcs tct tna tnb tnc tnn tns tnt tsa tsb tsc tsn tss tst tta ttb ttc ttn tts ttt