-er a-a a-b a-c a-t aaa aab aac aae aar aas aat aax ab- aba abb abc abe abr abs abt abx ac- aca acb acc ace acr acs act acx aea aeb aec aee aer aes aet aex ar- ara arb arc are arr ars art arx as- asa asb asc ase asr ass ast asx at- ata atb atc ate atr ats att atx ax- axa axe axr axs axt axx baa bab bac bae bar bas bat bax bba bbb bbc bbe bbr bbs bbt bbx bca bcb bcc bce bcr bcs bct bcx be- bea beb bec bee ber bes bet bex bra brb bre brr brs brt brx bsa bsb bsc bse bsr bss bst bsx bta btb btc bte btr bts btt btx bxb bxx c-- caa cab cac cae car cas cat cax cba cbb cbc cbe cbr cbs cbt cbx cca ccb ccc cce ccr ccs cct ccx ce- cea ceb cec cee cer ces cet cex cra crb crc cre crr crs crt crx csa csb csc cse csr css cst csx cta ctb ctc cte ctr cts ctt ctx cxc cxr cxs cxt cxx eaa eab eac eae ear eas eat eax eba ebb ebc ebe ebr ebs ebt ebx ec- eca ecb ecc ece ecr ecs ect ecx eea eeb eec eee eer ees eet eex era erb erc ere err ers ert es- esa esb esc ese esr ess est esx eta etb etc ete etr ets ett etx ex- exa exc exe exr exs ext exx ra- raa rab rac rae rar ras rat rax rba rbb rbc rbe rbr rbs rbt rbx rca rcb rcc rce rcr rcs rct rcx re- rea reb rec ree rer res ret rex rra rrb rrc rrr rrs rrt rsa rsb rsc rse rsr rss rst rsx rta rtb rtc rte rtr rts rtt rtx rxr rxs saa sab sac sae sar sas sat sax sba sbb sbc sbe sbr sbs sbt sbx sca scb scc sce scr scs sct scx se- sea seb sec see ser ses set sex sr- sra srb src sre srr srs srt srx ss- ssa ssb ssc sse ssr sss sst ssx sta stb stc ste str sts stt stx sxc sxs sxt t-x taa tab tac tae tar tas tat tax tba tbb tbc tbe tbr tbs tbt tca tcb tcc tce tcr tcs tct tcx te- tea teb tec tee ter tes tet tex tra trb trc tre trr trs trt trx tsa tsb tsc tse tsr tss tst tsx tta ttb ttc tte ttr tts ttt ttx txe txs txt xaa xac xar xas xat xbc xbe xbr xbx xcb xcr xcx xee xer xes xet xex xrc xrt xrx xsa xsb xsc xss xst xtc xtr xts xtx xxx