-er bbb bbe bbi bbk bbo bbr bbs bbt be- beb bee bei bek beo ber bes bet bi- bib bie bii bik bio bir bis bit bkb bke bkk bko bkr bks bkt bob boe boi bok boo bor bos bot brb bre bri brk bro brr brs brt bsb bse bsi bsk bso bsr bss bst btb bte bti btk bto btr bts btt ebb ebe ebi ebk ebo ebr ebs ebt eeb eee eek eeo eer ees eet eib eie eii eik eio eir eis eit ekb eke eki eko ekr eks ekt eo- eob eoe eoi eok eoo eor eos eot erb ere eri erk ero err ers ert es- esb ese esi esk eso esr ess est etb ete eti etk eto etr ets ett ibb ibe ibi ibk ibo ibr ibs ibt ie- iee iei iek ier ies iet iib iie iii iio iir iis iit ikb ike iki ikk iko ikr iks ikt io- iob ioe ioi ioo ior ios iot ir- irb ire iri irk iro irr irs irt is- isb ise isi isk iso isr iss ist itb ite iti itk ito its itt k-t kbb kbe kbi kbk kbo kbr kbs ke- keb kee kei kek keo ker kes ket kib kie kii kik kio kir kis kit kkb kke kki kkk kkr kks kkt kob koe koi kok koo kor kos kot kri krk kro krr krs krt ksb kse ksi ksk kso ksr kss kst ktb kte ktk kto ktr kts ktt o-i ob- obb obe obi obk obo obr obs obt oeb oee oei oeo oer oes oet oib oie oii oik oio oir ois oit okb oke oki okk oko okr oks oo- oob ooi ook ooo oor oos oot or- orb ore ori ork oro orr ors ort os- osb ose osi osk oso osr oss ost ot- otb ote oti otk oto otr ots ott rbb rbe rbi rbk rbo rbr rbs rbt re- reb ree rei rek reo rer res ret rib rie rii rik rio rir ris rit rkb rke rkk rko rks rkt rob roe roi rok roo ror ros rot rrb rri rrk rrr rrs rrt rsb rse rsi rsk rso rsr rss rst rtb rte rti rtk rto rtr rts rtt sbb sbe sbi sbk sbo sbr sbs sbt se- seb see sei sek seo ser ses set sib sie sii sik sio sir sis sit sk- skb ske ski skk sko skr sks skt sob soe soi sok soo sor sos sot sr- srb sre sri srk sro srr srs srt ss- ssb sse ssi ssk sso ssr sss sst stb ste sti stk sto str sts stt tbb tbe tbi tbk tbo tbr tbs tbt te- teb tee tei tek teo ter tes tet tib tie tii tik tio tir tis tit tkb tke tkk tko tkr tks tkt to- tob toe toi tok too tor tos tot trb tre tri trk tro trr trs trt tsb tse tsi tsk tso tsr tss tst ttb tte tti ttk tto ttr tts ttt