-er a-a a-b a-c a-t aaa aab aac aae aar aas aat ab- aba abb abc abe abr abs abt ac- aca acb acc ace acr acs act aea aeb aec aee aer aes aet ar- ara arb arc are arr ars art as- asa asb asc ase asr ass ast at- ata atb atc ate atr ats att baa bab bac bae bar bas bat bba bbb bbc bbe bbr bbs bbt bca bcb bcc bce bcr bcs bct be- bea beb bec bee ber bes bet bra brb bre brr brs brt bsa bsb bsc bse bsr bss bst bta btb btc bte btr bts btt c-- caa cab cac cae car cas cat cba cbb cbc cbe cbr cbs cbt cca ccb ccc cce ccr ccs cct ce- cea ceb cec cee cer ces cet cra crb crc cre crr crs crt csa csb csc cse csr css cst cta ctb ctc cte ctr cts ctt eaa eab eac eae ear eas eat eba ebb ebc ebe ebr ebs ebt ec- eca ecb ecc ece ecr ecs ect eea eeb eec eee eer ees eet era erb erc ere err ers ert es- esa esb esc ese esr ess est eta etb etc ete etr ets ett ra- raa rab rac rae rar ras rat rba rbb rbc rbe rbr rbs rbt rca rcb rcc rce rcr rcs rct re- rea reb rec ree rer res ret rra rrb rrc rrr rrs rrt rsa rsb rsc rse rsr rss rst rta rtb rtc rte rtr rts rtt saa sab sac sae sar sas sat sba sbb sbc sbe sbr sbs sbt sca scb scc sce scr scs sct se- sea seb sec see ser ses set sr- sra srb src sre srr srs srt ss- ssa ssb ssc sse ssr sss sst sta stb stc ste str sts stt taa tab tac tae tar tas tat tba tbb tbc tbe tbr tbs tbt tca tcb tcc tce tcr tcs tct te- tea teb tec tee ter tes tet tra trb trc tre trr trs trt tsa tsb tsc tse tsr tss tst tta ttb ttc tte ttr tts ttt