a-a a-b a-c a-t aaa aab aac aan aao aat ab- aba abb abc abn abo abt ac- aca acb acc acn aco act an- ana anb anc ann ano ant aoa aob aoc aon aoo aot at- ata atb atc atn ato att baa bab bac ban bao bat bba bbb bbc bbn bbo bbt bca bcb bcc bcn bco bct bna bnb bnc bnn bno bnt boa bob boc bon boo bot bta btb btc btn bto btt c-- caa cab cac can cao cat cba cbb cbc cbn cbo cbt cca ccb ccc ccn cco cct cn- cna cnb cnc cnn cno cnt co- coa cob coc con coo cot cta ctb ctc ctn cto ctt naa nab nac nan nao nat nba nbb nbc nbn nbo nbt nca ncb ncc ncn nco nct nna nnb nnc nnn nno nnt no- noa nob noc non noo not nta ntb ntc ntn nto ntt oaa oab oac oan oao oat ob- oba obb obc obn obo obt oc- oca ocb occ ocn oco oct on- ona onb onc onn ono ont oo- ooa oob ooc oon ooo oot ot- ota otb otc otn oto ott taa tab tac tan tao tat tba tbb tbc tbn tbo tbt tca tcb tcc tcn tco tct tna tnb tnc tnn tno tnt to- toa tob toc ton too tot tta ttb ttc ttn tto ttt