a-a a-b a-i a-t aaa aab aai aao aar aas aat ab- aba abb abi abo abr abs abt ai- aia aib aii aio air ais ait aoa aob aoi aoo aor aos aot ar- ara arb ari aro arr ars art as- asa asb asi aso asr ass ast at- ata atb ati ato atr ats att baa bab bai bao bar bas bat bba bbb bbi bbo bbr bbs bbt bi- bia bib bii bio bir bis bit boa bob boi boo bor bos bot bra brb bri bro brr brs brt bsa bsb bsi bso bsr bss bst bta btb bti bto btr bts btt ia- iaa iab iai iao iar ias iat iba ibb ibi ibo ibr ibs ibt iia iib iii iio iir iis iit io- ioa iob ioi ioo ior ios iot ir- ira irb iri iro irr irs irt is- isa isb isi iso isr iss ist ita itb iti ito its itt o-i oaa oab oai oao oar oas oat ob- oba obb obi obo obr obs obt oia oib oii oio oir ois oit oo- ooa oob ooi ooo oor oos oot or- ora orb ori oro orr ors ort os- osa osb osi oso osr oss ost ot- ota otb oti oto otr ots ott ra- raa rab rai rao rar ras rat rba rbb rbi rbo rbr rbs rbt ria rib rii rio rir ris rit roa rob roi roo ror ros rot rra rrb rri rrr rrs rrt rsa rsb rsi rso rsr rss rst rta rtb rti rto rtr rts rtt saa sab sai sao sar sas sat sba sbb sbi sbo sbr sbs sbt sia sib sii sio sir sis sit soa sob soi soo sor sos sot sr- sra srb sri sro srr srs srt ss- ssa ssb ssi sso ssr sss sst sta stb sti sto str sts stt taa tab tai tao tar tas tat tba tbb tbi tbo tbr tbs tbt tia tib tii tio tir tis tit to- toa tob toi too tor tos tot tra trb tri tro trr trs trt tsa tsb tsi tso tsr tss tst tta ttb tti tto ttr tts ttt