a-a a-b a-t a-z aaa aab aaf aao aat aaz ab- aba abb abf abo abt abz af- afa afb aff afo aft afz aoa aob aof aoo aot at- ata atb atf ato att atz az- aza azb azf azo azt azz baa bab baf bao bat baz bba bbb bbf bbo bbt bfa bfb bff bfo bft bfz boa bob bof boo bot boz bta btb btf bto btt btz bza bzf bzo bzz faa fab faf fao fat faz fba fbb fbf fbo fbt ffa fff ffo fft ffz foa fob fof foo fot foz fta ftb ftf fto ftt ftz oaa oab oaf oao oat ob- oba obb obf obo obt of- ofa ofb off ofo oft ofz oo- ooa oob oof ooo oot ot- ota otb otf oto ott otz oza ozo ozt ozz taa tab taf tao tat taz tba tbb tbf tbo tbt tbz tfa tfb tff tfo tft to- toa tob tof too tot toz tta ttb ttf tto ttt tza tzf zaa zab zaf zao zat zaz zbb zbt zfa zo- zoa zob zof zoo zot zta zzt zzz