a-a a-b a-c a-t aaa aab aac aae aan aat ab- aba abb abc abe abn abt ac- aca acb acc ace acn act aea aeb aec aee aen aet an- ana anb anc ane ann ant at- ata atb atc ate atn att baa bab bac bae ban bat bba bbb bbc bbe bbn bbt bca bcb bcc bce bcn bct be- bea beb bec bee ben bet bna bnb bnc bne bnn bnt bta btb btc bte btn btt c-- caa cab cac cae can cat cba cbb cbc cbe cbn cbt cca ccb ccc cce ccn cct ce- cea ceb cec cee cen cet cn- cna cnb cnc cne cnn cnt cta ctb ctc cte ctn ctt eaa eab eac eae ean eat eba ebb ebc ebe ebn ebt ec- eca ecb ecc ece ecn ect eea eeb eec eee een eet en- ena enb enc ene enn ent eta etb etc ete etn ett naa nab nac nae nan nat nba nbb nbc nbe nbn nbt nca ncb ncc nce ncn nct ne- nea neb nec nee nen net nna nnb nnc nne nnn nnt nta ntb ntc nte ntn ntt taa tab tac tae tan tat tba tbb tbc tbe tbn tbt tca tcb tcc tce tcn tct te- tea teb tec tee ten tet tna tnb tnc tne tnn tnt tta ttb ttc tte ttn ttt