-er a-a a-c a-t aaa aac aae aar aas aat aax ac- aca acc ace acr acs act acx aea aec aee aer aes aet aex ar- ara arc are arr ars art arx as- asa asc ase asr ass ast asx at- ata atc ate atr ats att atx ax- axa axe axr axs axt axx c-- caa cac cae car cas cat cax cca ccc cce ccr ccs cct ccx ce- cea cec cee cer ces cet cex cra crc cre crr crs crt crx csa csc cse csr css cst csx cta ctc cte ctr cts ctt ctx cxc cxr cxs cxt cxx eaa eac eae ear eas eat eax ec- eca ecc ece ecr ecs ect ecx eea eec eee eer ees eet eex era erc ere err ers ert es- esa esc ese esr ess est esx eta etc ete etr ets ett etx ex- exa exc exe exr exs ext exx ra- raa rac rae rar ras rat rax rca rcc rce rcr rcs rct rcx re- rea rec ree rer res ret rex rra rrc rrr rrs rrt rsa rsc rse rsr rss rst rsx rta rtc rte rtr rts rtt rtx rxr rxs saa sac sae sar sas sat sax sca scc sce scr scs sct scx se- sea sec see ser ses set sex sr- sra src sre srr srs srt srx ss- ssa ssc sse ssr sss sst ssx sta stc ste str sts stt stx sxc sxs sxt t-x taa tac tae tar tas tat tax tca tcc tce tcr tcs tct tcx te- tea tec tee ter tes tet tex tra trc tre trr trs trt trx tsa tsc tse tsr tss tst tsx tta ttc tte ttr tts ttt ttx txe txs txt xaa xac xar xas xat xcr xcx xee xer xes xet xex xrc xrt xrx xsa xsc xss xst xtc xtr xts xtx xxx