-er bbb bbe bbr bbs bbt be- beb bee ber bes bet brb bre brr brs brt bsb bse bsr bss bst btb bte btr bts btt ebb ebe ebr ebs ebt eeb eee eer ees eet erb ere err ers ert es- esb ese esr ess est etb ete etr ets ett rbb rbe rbr rbs rbt re- reb ree rer res ret rrb rrr rrs rrt rsb rse rsr rss rst rtb rte rtr rts rtt sbb sbe sbr sbs sbt se- seb see ser ses set sr- srb sre srr srs srt ss- ssb sse ssr sss sst stb ste str sts stt tbb tbe tbr tbs tbt te- teb tee ter tes tet trb tre trr trs trt tsb tse tsr tss tst ttb tte ttr tts ttt