a-a a-b a-t aaa aab aan aat aay ab- aba abb abn abt aby an- ana anb ann ant any at- ata atb atn att ay- aya ayn ayt baa bab ban bat bay bba bbb bbn bbt bby bna bnb bnn bnt bta btb btn btt bty by- bya byn byt naa nab nan nat nay nba nbb nbn nbt nna nnb nnn nnt nta ntb ntn ntt nya nyn nyt nyy taa tab tan tat tay tba tbb tbn tbt tna tnb tnn tnt tta ttb ttn ttt tty tya tyn tyt yaa yab yan yat yay yby yna ynn yny yta ytn ytt yyb yyt yyy