-er bbb bbe bbk bbr bbs bbt be- beb bee bek ber bes bet bkb bke bkk bkr bks bkt brb bre brk brr brs brt bsb bse bsk bsr bss bst btb bte btk btr bts btt ebb ebe ebk ebr ebs ebt eeb eee eek eer ees eet ekb eke ekr eks ekt erb ere erk err ers ert es- esb ese esk esr ess est etb ete etk etr ets ett k-t kbb kbe kbk kbr kbs ke- keb kee kek ker kes ket kkb kke kkk kkr kks kkt krk krr krs krt ksb kse ksk ksr kss kst ktb kte ktk ktr kts ktt rbb rbe rbk rbr rbs rbt re- reb ree rek rer res ret rkb rke rkk rks rkt rrb rrk rrr rrs rrt rsb rse rsk rsr rss rst rtb rte rtk rtr rts rtt sbb sbe sbk sbr sbs sbt se- seb see sek ser ses set sk- skb ske skk skr sks skt sr- srb sre srk srr srs srt ss- ssb sse ssk ssr sss sst stb ste stk str sts stt tbb tbe tbk tbr tbs tbt te- teb tee tek ter tes tet tkb tke tkk tkr tks tkt trb tre trk trr trs trt tsb tse tsk tsr tss tst ttb tte ttk ttr tts ttt