-er a-a a-b a-c a-t aaa aab aac aae aar aat aax ab- aba abb abc abe abr abt abx ac- aca acb acc ace acr act acx aea aeb aec aee aer aet aex ar- ara arb arc are arr art arx at- ata atb atc ate atr att atx ax- axa axe axr axt axx baa bab bac bae bar bat bax bba bbb bbc bbe bbr bbt bbx bca bcb bcc bce bcr bct bcx be- bea beb bec bee ber bet bex bra brb bre brr brt brx bta btb btc bte btr btt btx bxb bxx c-- caa cab cac cae car cat cax cba cbb cbc cbe cbr cbt cbx cca ccb ccc cce ccr cct ccx ce- cea ceb cec cee cer cet cex cra crb crc cre crr crt crx cta ctb ctc cte ctr ctt ctx cxc cxr cxt cxx eaa eab eac eae ear eat eax eba ebb ebc ebe ebr ebt ebx ec- eca ecb ecc ece ecr ect ecx eea eeb eec eee eer eet eex era erb erc ere err ert eta etb etc ete etr ett etx ex- exa exc exe exr ext exx ra- raa rab rac rae rar rat rax rba rbb rbc rbe rbr rbt rbx rca rcb rcc rce rcr rct rcx re- rea reb rec ree rer ret rex rra rrb rrc rrr rrt rta rtb rtc rte rtr rtt rtx rxr t-x taa tab tac tae tar tat tax tba tbb tbc tbe tbr tbt tca tcb tcc tce tcr tct tcx te- tea teb tec tee ter tet tex tra trb trc tre trr trt trx tta ttb ttc tte ttr ttt ttx txe txt xaa xac xar xat xbc xbe xbr xbx xcb xcr xcx xee xer xet xex xrc xrt xrx xtc xtr xtx xxx