a-a a-b a-i a-z aaa aab aai aao aaz ab- aba abb abi abo abz ai- aia aib aii aio aiz aoa aob aoi aoo az- aza azb azi azo azz baa bab bai bao baz bba bbb bbi bbo bi- bia bib bii bio biz boa bob boi boo boz bza bzo bzz ia- iaa iab iai iao iaz iba ibb ibi ibo ibz iia iib iii iio io- ioa iob ioi ioo iza izi izo izz o-i oaa oab oai oao ob- oba obb obi obo oia oib oii oio oiz oo- ooa oob ooi ooo oza ozo ozz zaa zab zai zao zaz zbb zia zib zio ziz zo- zoa zob zoi zoo zzz