a-a a-b a-c a-t aaa aab aac aao aat aay ab- aba abb abc abo abt aby ac- aca acb acc aco act acy aoa aob aoc aoo aot at- ata atb atc ato att ay- aya ayc ayo ayt baa bab bac bao bat bay bba bbb bbc bbo bbt bby bca bcb bcc bco bct bcy boa bob boc boo bot boy bta btb btc bto btt bty by- bya byc byo byt c-- caa cab cac cao cat cay cba cbb cbc cbo cbt cby cca ccb ccc cco cct co- coa cob coc coo cot coy cta ctb ctc cto ctt cty cya cyb cyc cyo cyt oaa oab oac oao oat ob- oba obb obc obo obt oby oc- oca ocb occ oco oct oo- ooa oob ooc ooo oot ot- ota otb otc oto ott oya oyo taa tab tac tao tat tay tba tbb tbc tbo tbt tca tcb tcc tco tct to- toa tob toc too tot toy tta ttb ttc tto ttt tty tya tyc tyo tyt yaa yab yac yao yat yay ybc yby yca ycc yco ycy yob yoc yoo yot yoy yta ytc yto ytt yyb yyc yyt yyy