a-a a-b a-c a-t aaa aab aac aae aan aao aat ab- aba abb abc abe abn abo abt ac- aca acb acc ace acn aco act aea aeb aec aee aen aeo aet an- ana anb anc ane ann ano ant aoa aob aoc aoe aon aoo aot at- ata atb atc ate atn ato att baa bab bac bae ban bao bat bba bbb bbc bbe bbn bbo bbt bca bcb bcc bce bcn bco bct be- bea beb bec bee ben beo bet bna bnb bnc bne bnn bno bnt boa bob boc boe bon boo bot bta btb btc bte btn bto btt c-- caa cab cac cae can cao cat cba cbb cbc cbe cbn cbo cbt cca ccb ccc cce ccn cco cct ce- cea ceb cec cee cen ceo cet cn- cna cnb cnc cne cnn cno cnt co- coa cob coc coe con coo cot cta ctb ctc cte ctn cto ctt eaa eab eac eae ean eao eat eba ebb ebc ebe ebn ebo ebt ec- eca ecb ecc ece ecn eco ect eea eeb eec eee een eeo eet en- ena enb enc ene enn eno ent eo- eoa eob eoc eoe eon eoo eot eta etb etc ete etn eto ett naa nab nac nae nan nao nat nba nbb nbc nbe nbn nbo nbt nca ncb ncc nce ncn nco nct ne- nea neb nec nee nen neo net nna nnb nnc nne nnn nno nnt no- noa nob noc noe non noo not nta ntb ntc nte ntn nto ntt oaa oab oac oae oan oao oat ob- oba obb obc obe obn obo obt oc- oca ocb occ ocn oco oct oea oeb oec oee oen oeo oet on- ona onb onc one onn ono ont oo- ooa oob ooc oon ooo oot ot- ota otb otc ote otn oto ott taa tab tac tae tan tao tat tba tbb tbc tbe tbn tbo tbt tca tcb tcc tce tcn tco tct te- tea teb tec tee ten teo tet tna tnb tnc tne tnn tno tnt to- toa tob toc toe ton too tot tta ttb ttc tte ttn tto ttt