a-a a-b a-c a-t aaa aab aac aao aat ab- aba abb abc abo abt ac- aca acb acc aco act aoa aob aoc aoo aot at- ata atb atc ato att baa bab bac bao bat bba bbb bbc bbo bbt bca bcb bcc bco bct boa bob boc boo bot bta btb btc bto btt c-- caa cab cac cao cat cba cbb cbc cbo cbt cca ccb ccc cco cct co- coa cob coc coo cot cta ctb ctc cto ctt oaa oab oac oao oat ob- oba obb obc obo obt oc- oca ocb occ oco oct oo- ooa oob ooc ooo oot ot- ota otb otc oto ott taa tab tac tao tat tba tbb tbc tbo tbt tca tcb tcc tco tct to- toa tob toc too tot tta ttb ttc tto ttt