-er a-a a-b aaa aab aae aan aar aas aax ab- aba abb abe abn abr abs abx aea aeb aee aen aer aes aex an- ana anb ane ann anr ans anx ar- ara arb are arn arr ars arx as- asa asb ase asn asr ass asx ax- axa axe axn axr axs axx baa bab bae ban bar bas bax bba bbb bbe bbn bbr bbs bbx be- bea beb bee ben ber bes bex bna bnb bne bnn bnr bns bnx bra brb bre brn brr brs brx bsa bsb bse bsn bsr bss bsx bxb bxn bxx eaa eab eae ean ear eas eax eba ebb ebe ebn ebr ebs ebx eea eeb eee een eer ees eex en- ena enb ene enn enr ens era erb ere ern err ers es- esa esb ese esn esr ess esx ex- exa exe exr exs exx naa nab nae nan nar nas nax nba nbb nbe nbn nbr nbs nbx ne- nea neb nee nen ner nes nex nna nnb nne nnn nns nra nrb nre nrn nrr nrs nrx nsa nsb nse nsn nsr nss nsx ra- raa rab rae ran rar ras rax rba rbb rbe rbn rbr rbs rbx re- rea reb ree ren rer res rex rna rnb rnn rnr rns rra rrb rrn rrr rrs rsa rsb rse rsn rsr rss rsx rxr rxs saa sab sae san sar sas sax sba sbb sbe sbn sbr sbs sbx se- sea seb see sen ser ses sex sna snb sne snn snr sns sr- sra srb sre srn srr srs srx ss- ssa ssb sse ssn ssr sss ssx sxn sxs xaa xan xar xas xbe xbr xbx xee xen xer xes xex xna xns xrx xsa xsb xss xxx