-er a-a a-c a-t aaa aac aae aar aat aax ac- aca acc ace acr act acx aea aec aee aer aet aex ar- ara arc are arr art arx at- ata atc ate atr att atx ax- axa axe axr axt axx c-- caa cac cae car cat cax cca ccc cce ccr cct ccx ce- cea cec cee cer cet cex cra crc cre crr crt crx cta ctc cte ctr ctt ctx cxc cxr cxt cxx eaa eac eae ear eat eax ec- eca ecc ece ecr ect ecx eea eec eee eer eet eex era erc ere err ert eta etc ete etr ett etx ex- exa exc exe exr ext exx ra- raa rac rae rar rat rax rca rcc rce rcr rct rcx re- rea rec ree rer ret rex rra rrc rrr rrt rta rtc rte rtr rtt rtx rxr t-x taa tac tae tar tat tax tca tcc tce tcr tct tcx te- tea tec tee ter tet tex tra trc tre trr trt trx tta ttc tte ttr ttt ttx txe txt xaa xac xar xat xcr xcx xee xer xet xex xrc xrt xrx xtc xtr xtx xxx