-er bbb bbe bbi bbk bbo bbr bbs be- beb bee bei bek beo ber bes bi- bib bie bii bik bio bir bis bkb bke bkk bko bkr bks bob boe boi bok boo bor bos brb bre bri brk bro brr brs bsb bse bsi bsk bso bsr bss ebb ebe ebi ebk ebo ebr ebs eeb eee eek eeo eer ees eib eie eii eik eio eir eis ekb eke eki eko ekr eks eo- eob eoe eoi eok eoo eor eos erb ere eri erk ero err ers es- esb ese esi esk eso esr ess ibb ibe ibi ibk ibo ibr ibs ie- iee iei iek ier ies iib iie iii iio iir iis ikb ike iki ikk iko ikr iks io- iob ioe ioi ioo ior ios ir- irb ire iri irk iro irr irs is- isb ise isi isk iso isr iss kbb kbe kbi kbk kbo kbr kbs ke- keb kee kei kek keo ker kes kib kie kii kik kio kir kis kkb kke kki kkk kkr kks kob koe koi kok koo kor kos kri krk kro krr krs ksb kse ksi ksk kso ksr kss o-i ob- obb obe obi obk obo obr obs oeb oee oei oeo oer oes oib oie oii oik oio oir ois okb oke oki okk oko okr oks oo- oob ooi ook ooo oor oos or- orb ore ori ork oro orr ors os- osb ose osi osk oso osr oss rbb rbe rbi rbk rbo rbr rbs re- reb ree rei rek reo rer res rib rie rii rik rio rir ris rkb rke rkk rko rks rob roe roi rok roo ror ros rrb rri rrk rrr rrs rsb rse rsi rsk rso rsr rss sbb sbe sbi sbk sbo sbr sbs se- seb see sei sek seo ser ses sib sie sii sik sio sir sis sk- skb ske ski skk sko skr sks sob soe soi sok soo sor sos sr- srb sre sri srk sro srr srs ss- ssb sse ssi ssk sso ssr sss