-er bbb bbe bbf bbi bbk bbo bbr bbs be- beb bee bef bei bek beo ber bes bfb bfe bff bfi bfo bfr bfs bi- bib bie bif bii bik bio bir bis bkb bke bkf bkk bko bkr bks bob boe bof boi bok boo bor bos brb bre brf bri brk bro brr brs bsb bse bsf bsi bsk bso bsr bss ebb ebe ebf ebi ebk ebo ebr ebs eeb eee eef eek eeo eer ees ef- efb efe eff efi efo efr efs eib eie eif eii eik eio eir eis ekb eke ekf eki eko ekr eks eo- eob eoe eof eoi eok eoo eor eos erb ere erf eri erk ero err ers es- esb ese esf esi esk eso esr ess fbb fbe fbf fbi fbk fbo fbr fbs feb fee fef fei fek feo fer fes ffe fff ffi ffk ffo ffr ffs fib fie fif fii fik fir fis fkb fkf fki fkk fob foe fof foi fok foo for fos frb fre frf fri frk fro frr frs fsb fse fsf fsi fsk fso fsr fss i-f ibb ibe ibf ibi ibk ibo ibr ibs ie- iee ief iei iek ier ies ifb ife iff ifi ifo ifr ifs iib iie iif iii iio iir iis ikb ike ikf iki ikk iko ikr iks io- iob ioe iof ioi ioo ior ios ir- irb ire irf iri irk iro irr irs is- isb ise isf isi isk iso isr iss kbb kbe kbf kbi kbk kbo kbr kbs ke- keb kee kef kei kek keo ker kes kff kfi kfo kfs kib kie kif kii kik kio kir kis kkb kke kki kkk kkr kks kob koe kof koi kok koo kor kos krf kri krk kro krr krs ksb kse ksf ksi ksk kso ksr kss o-i ob- obb obe obf obi obk obo obr obs oeb oee oef oei oeo oer oes of- ofb ofe off ofi ofo ofr ofs oib oie oif oii oik oio oir ois okb oke oki okk oko okr oks oo- oob oof ooi ook ooo oor oos or- orb ore orf ori ork oro orr ors os- osb ose osf osi osk oso osr oss rbb rbe rbf rbi rbk rbo rbr rbs re- reb ree ref rei rek reo rer res rfb rfe rff rfi rfk rfo rfr rfs rib rie rif rii rik rio rir ris rkb rke rkf rkk rko rks rob roe rof roi rok roo ror ros rrb rrf rri rrk rrr rrs rsb rse rsf rsi rsk rso rsr rss sbb sbe sbf sbi sbk sbo sbr sbs se- seb see sef sei sek seo ser ses sfb sfe sff sfi sfk sfo sfr sfs sib sie sif sii sik sio sir sis sk- skb ske skf ski skk sko skr sks sob soe sof soi sok soo sor sos sr- srb sre srf sri srk sro srr srs ss- ssb sse ssf ssi ssk sso ssr sss