-er a-a a-b a-c a-t aaa aab aac aae aak aar aat aax ab- aba abb abc abe abk abr abt abx ac- aca acb acc ace ack acr act acx aea aeb aec aee aek aer aet aex aka akb akc ake akk akr ar- ara arb arc are ark arr art arx at- ata atb atc ate atr att atx ax- axa axe axk axr axt axx baa bab bac bae bak bar bat bax bba bbb bbc bbe bbk bbr bbt bbx bca bcb bcc bce bck bcr bct bcx be- bea beb bec bee bek ber bet bex bka bkb bkc bke bkk bkr bkt bkx bra brb bre brk brr brt brx bta btb btc bte btk btr btt btx bxb bxx c-- caa cab cac cae cak car cat cax cba cbb cbc cbe cbk cbr cbt cbx cca ccb ccc cce cck ccr cct ccx ce- cea ceb cec cee cek cer cet cex cka ckb ckc ckt ckx cra crb crc cre crk crr crt crx cta ctb ctc cte ctk ctr ctt ctx cxc cxk cxr cxt cxx eaa eab eac eae eak ear eat eax eba ebb ebc ebe ebk ebr ebt ebx ec- eca ecb ecc ece eck ecr ect ecx eea eeb eec eee eek eer eet eex eka ekb ekc eke ekr ekt era erb erc ere erk err ert eta etb etc ete etk etr ett etx ex- exa exc exe exr ext exx k-t ka- kaa kab kac kae kak kar kat kax kba kbb kbc kbe kbk kbr kbx kca kcb kcc kce kck kcr kct kcx ke- kea keb kec kee kek ker ket kex kkb kkc kke kkk kkr kkt kra krc krk krr krt kta ktb ktc kte ktk ktr ktt ra- raa rab rac rae rak rar rat rax rba rbb rbc rbe rbk rbr rbt rbx rca rcb rcc rce rcr rct rcx re- rea reb rec ree rek rer ret rex rkb rkc rke rkk rkt rra rrb rrc rrk rrr rrt rta rtb rtc rte rtk rtr rtt rtx rxr t-x taa tab tac tae tak tar tat tax tba tbb tbc tbe tbk tbr tbt tca tcb tcc tce tck tcr tct tcx te- tea teb tec tee tek ter tet tex tka tkb tkc tke tkk tkr tkt tra trb trc tre trk trr trt trx tta ttb ttc tte ttk ttr ttt ttx txe txk txt xaa xac xak xar xat xbc xbe xbr xbx xcb xcr xcx xee xer xet xex xkb xke xrc xrt xrx xtc xtr xtx xxx