a-a a-b a-i a-t aaa aab aai aar aat ab- aba abb abi abr abt ai- aia aib aii air ait ar- ara arb ari arr art at- ata atb ati atr att baa bab bai bar bat bba bbb bbi bbr bbt bi- bia bib bii bir bit bra brb bri brr brt bta btb bti btr btt ia- iaa iab iai iar iat iba ibb ibi ibr ibt iia iib iii iir iit ir- ira irb iri irr irt ita itb iti itt ra- raa rab rai rar rat rba rbb rbi rbr rbt ria rib rii rir rit rra rrb rri rrr rrt rta rtb rti rtr rtt taa tab tai tar tat tba tbb tbi tbr tbt tia tib tii tir tit tra trb tri trr trt tta ttb tti ttr ttt