a-a a-b a-t a-z aaa aab aao aat aaz ab- aba abb abo abt abz aoa aob aoo aot at- ata atb ato att atz az- aza azb azo azt azz baa bab bao bat baz bba bbb bbo bbt boa bob boo bot boz bta btb bto btt btz bza bzo bzz oaa oab oao oat ob- oba obb obo obt oo- ooa oob ooo oot ot- ota otb oto ott otz oza ozo ozt ozz taa tab tao tat taz tba tbb tbo tbt tbz to- toa tob too tot toz tta ttb tto ttt tza zaa zab zao zat zaz zbb zbt zo- zoa zob zoo zot zta zzt zzz