-er a-a a-b a-i a-t aaa aab aae aai aar aas aat aax ab- aba abb abe abi abr abs abt abx aea aeb aee aei aer aes aet aex ai- aia aib aie aii air ais ait aix ar- ara arb are ari arr ars art arx as- asa asb ase asi asr ass ast asx at- ata atb ate ati atr ats att atx ax- axa axe axi axr axs axt axx baa bab bae bai bar bas bat bax bba bbb bbe bbi bbr bbs bbt bbx be- bea beb bee bei ber bes bet bex bi- bia bib bie bii bir bis bit bix bra brb bre bri brr brs brt brx bsa bsb bse bsi bsr bss bst bsx bta btb bte bti btr bts btt btx bxb bxi bxx eaa eab eae eai ear eas eat eax eba ebb ebe ebi ebr ebs ebt ebx eea eeb eee eer ees eet eex eia eib eie eii eir eis eit eix era erb ere eri err ers ert es- esa esb ese esi esr ess est esx eta etb ete eti etr ets ett etx ex- exa exe exi exr exs ext exx ia- iaa iab iae iai iar ias iat iba ibb ibe ibi ibr ibs ibt ibx ie- iea iee iei ier ies iet iex iia iib iie iii iir iis iit iix ir- ira irb ire iri irr irs irt irx is- isa isb ise isi isr iss ist ita itb ite iti its itt itx ixe ixi ra- raa rab rae rai rar ras rat rax rba rbb rbe rbi rbr rbs rbt rbx re- rea reb ree rei rer res ret rex ria rib rie rii rir ris rit rix rra rrb rri rrr rrs rrt rsa rsb rse rsi rsr rss rst rsx rta rtb rte rti rtr rts rtt rtx rxr rxs saa sab sae sai sar sas sat sax sba sbb sbe sbi sbr sbs sbt sbx se- sea seb see sei ser ses set sex sia sib sie sii sir sis sit six sr- sra srb sre sri srr srs srt srx ss- ssa ssb sse ssi ssr sss sst ssx sta stb ste sti str sts stt stx sxi sxs sxt t-x taa tab tae tai tar tas tat tax tba tbb tbe tbi tbr tbs tbt te- tea teb tee tei ter tes tet tex tia tib tie tii tir tis tit tix tra trb tre tri trr trs trt trx tsa tsb tse tsi tsr tss tst tsx tta ttb tte tti ttr tts ttt ttx txe txi txs txt xaa xar xas xat xbe xbr xbx xee xer xes xet xex xia xie xii xis xit xix xrt xrx xsa xsb xsi xss xst xti xtr xts xtx xxi xxx