-er a-a a-b aaa aab aae aak aan aao aar aas ab- aba abb abe abk abn abo abr abs aea aeb aee aek aen aeo aer aes aka akb ake akk akn ako akr aks an- ana anb ane ank ann ano anr ans aoa aob aoe aok aon aoo aor aos ar- ara arb are ark arn aro arr ars as- asa asb ase ask asn aso asr ass baa bab bae bak ban bao bar bas bba bbb bbe bbk bbn bbo bbr bbs be- bea beb bee bek ben beo ber bes bka bkb bke bkk bkn bko bkr bks bna bnb bne bnk bnn bno bnr bns boa bob boe bok bon boo bor bos bra brb bre brk brn bro brr brs bsa bsb bse bsk bsn bso bsr bss eaa eab eae eak ean eao ear eas eba ebb ebe ebk ebn ebo ebr ebs eea eeb eee eek een eeo eer ees eka ekb eke eko ekr eks en- ena enb ene enk enn eno enr ens eo- eoa eob eoe eok eon eoo eor eos era erb ere erk ern ero err ers es- esa esb ese esk esn eso esr ess ka- kaa kab kae kak kan kao kar kas kba kbb kbe kbk kbn kbo kbr kbs ke- kea keb kee kek ken keo ker kes kkb kke kkk kkn kkr kks kn- kna kne knk knn kno knr koa kob koe kok kon koo kor kos kra krk krn kro krr krs ksa ksb kse ksk ksn kso ksr kss naa nab nae nak nan nao nar nas nba nbb nbe nbk nbn nbo nbr nbs ne- nea neb nee nek nen neo ner nes nka nke nkk nkn nko nkr nks nna nnb nne nnk nnn nno nns no- noa nob noe nok non noo nor nos nra nrb nre nrk nrn nro nrr nrs nsa nsb nse nsk nsn nso nsr nss oaa oab oae oak oan oao oar oas ob- oba obb obe obk obn obo obr obs oea oeb oee oen oeo oer oes oka okb oke okk oko okr oks on- ona onb one onk onn ono onr ons oo- ooa oob ook oon ooo oor oos or- ora orb ore ork orn oro orr ors os- osa osb ose osk osn oso osr oss ra- raa rab rae rak ran rao rar ras rba rbb rbe rbk rbn rbo rbr rbs re- rea reb ree rek ren reo rer res rkb rke rkk rko rks rna rnb rnn rno rnr rns roa rob roe rok ron roo ror ros rra rrb rrk rrn rrr rrs rsa rsb rse rsk rsn rso rsr rss saa sab sae sak san sao sar sas sba sbb sbe sbk sbn sbo sbr sbs se- sea seb see sek sen seo ser ses sk- ska skb ske skk sko skr sks sna snb sne snk snn sno snr sns soa sob soe sok son soo sor sos sr- sra srb sre srk srn sro srr srs ss- ssa ssb sse ssk ssn sso ssr sss