-er a-a a-b a-t aaa aab aae aak aar aat aax ab- aba abb abe abk abr abt abx aea aeb aee aek aer aet aex aka akb ake akk akr ar- ara arb are ark arr art arx at- ata atb ate atr att atx ax- axa axe axk axr axt axx baa bab bae bak bar bat bax bba bbb bbe bbk bbr bbt bbx be- bea beb bee bek ber bet bex bka bkb bke bkk bkr bkt bkx bra brb bre brk brr brt brx bta btb bte btk btr btt btx bxb bxx eaa eab eae eak ear eat eax eba ebb ebe ebk ebr ebt ebx eea eeb eee eek eer eet eex eka ekb eke ekr ekt era erb ere erk err ert eta etb ete etk etr ett etx ex- exa exe exr ext exx k-t ka- kaa kab kae kak kar kat kax kba kbb kbe kbk kbr kbx ke- kea keb kee kek ker ket kex kkb kke kkk kkr kkt kra krk krr krt kta ktb kte ktk ktr ktt ra- raa rab rae rak rar rat rax rba rbb rbe rbk rbr rbt rbx re- rea reb ree rek rer ret rex rkb rke rkk rkt rra rrb rrk rrr rrt rta rtb rte rtk rtr rtt rtx rxr t-x taa tab tae tak tar tat tax tba tbb tbe tbk tbr tbt te- tea teb tee tek ter tet tex tka tkb tke tkk tkr tkt tra trb tre trk trr trt trx tta ttb tte ttk ttr ttt ttx txe txk txt xaa xak xar xat xbe xbr xbx xee xer xet xex xkb xke xrt xrx xtr xtx xxx