a-a a-b a-i a-t aaa aab aai aao aat ab- aba abb abi abo abt ai- aia aib aii aio ait aoa aob aoi aoo aot at- ata atb ati ato att baa bab bai bao bat bba bbb bbi bbo bbt bi- bia bib bii bio bit boa bob boi boo bot bta btb bti bto btt ia- iaa iab iai iao iat iba ibb ibi ibo ibt iia iib iii iio iit io- ioa iob ioi ioo iot ita itb iti ito itt o-i oaa oab oai oao oat ob- oba obb obi obo obt oia oib oii oio oit oo- ooa oob ooi ooo oot ot- ota otb oti oto ott taa tab tai tao tat tba tbb tbi tbo tbt tia tib tii tio tit to- toa tob toi too tot tta ttb tti tto ttt