-er a-a a-b a-t aaa aab aae aar aas aat aax ab- aba abb abe abr abs abt abx aea aeb aee aer aes aet aex ar- ara arb are arr ars art arx as- asa asb ase asr ass ast asx at- ata atb ate atr ats att atx ax- axa axe axr axs axt axx baa bab bae bar bas bat bax bba bbb bbe bbr bbs bbt bbx be- bea beb bee ber bes bet bex bra brb bre brr brs brt brx bsa bsb bse bsr bss bst bsx bta btb bte btr bts btt btx bxb bxx eaa eab eae ear eas eat eax eba ebb ebe ebr ebs ebt ebx eea eeb eee eer ees eet eex era erb ere err ers ert es- esa esb ese esr ess est esx eta etb ete etr ets ett etx ex- exa exe exr exs ext exx ra- raa rab rae rar ras rat rax rba rbb rbe rbr rbs rbt rbx re- rea reb ree rer res ret rex rra rrb rrr rrs rrt rsa rsb rse rsr rss rst rsx rta rtb rte rtr rts rtt rtx rxr rxs saa sab sae sar sas sat sax sba sbb sbe sbr sbs sbt sbx se- sea seb see ser ses set sex sr- sra srb sre srr srs srt srx ss- ssa ssb sse ssr sss sst ssx sta stb ste str sts stt stx sxs sxt t-x taa tab tae tar tas tat tax tba tbb tbe tbr tbs tbt te- tea teb tee ter tes tet tex tra trb tre trr trs trt trx tsa tsb tse tsr tss tst tsx tta ttb tte ttr tts ttt ttx txe txs txt xaa xar xas xat xbe xbr xbx xee xer xes xet xex xrt xrx xsa xsb xss xst xtr xts xtx xxx