-er a-a a-b a-t aaa aab aae aan aar aat aax ab- aba abb abe abn abr abt abx aea aeb aee aen aer aet aex an- ana anb ane ann anr ant anx ar- ara arb are arn arr art arx at- ata atb ate atn atr att atx ax- axa axe axn axr axt axx baa bab bae ban bar bat bax bba bbb bbe bbn bbr bbt bbx be- bea beb bee ben ber bet bex bna bnb bne bnn bnr bnt bnx bra brb bre brn brr brt brx bta btb bte btn btr btt btx bxb bxn bxx eaa eab eae ean ear eat eax eba ebb ebe ebn ebr ebt ebx eea eeb eee een eer eet eex en- ena enb ene enn enr ent era erb ere ern err ert eta etb ete etn etr ett etx ex- exa exe exr ext exx naa nab nae nan nar nat nax nba nbb nbe nbn nbr nbt nbx ne- nea neb nee nen ner net nex nna nnb nne nnn nnt nra nrb nre nrn nrr nrt nrx nta ntb nte ntn ntr ntt ntx nxt ra- raa rab rae ran rar rat rax rba rbb rbe rbn rbr rbt rbx re- rea reb ree ren rer ret rex rna rnb rnn rnr rnt rra rrb rrn rrr rrt rta rtb rte rtn rtr rtt rtx rxr t-x taa tab tae tan tar tat tax tba tbb tbe tbn tbr tbt te- tea teb tee ten ter tet tex tna tnb tne tnn tnr tnt tnx tra trb tre trn trr trt trx tta ttb tte ttn ttr ttt ttx txe txn txt xaa xan xar xat xbe xbr xbx xee xen xer xet xex xna xrt xrx xtr xtx xxx