-er bbb bbe bbo bbr bbs be- beb bee beo ber bes bob boe boo bor bos brb bre bro brr brs bsb bse bso bsr bss ebb ebe ebo ebr ebs eeb eee eeo eer ees eo- eob eoe eoo eor eos erb ere ero err ers es- esb ese eso esr ess ob- obb obe obo obr obs oeb oee oeo oer oes oo- oob ooo oor oos or- orb ore oro orr ors os- osb ose oso osr oss rbb rbe rbo rbr rbs re- reb ree reo rer res rob roe roo ror ros rrb rrr rrs rsb rse rso rsr rss sbb sbe sbo sbr sbs se- seb see seo ser ses sob soe soo sor sos sr- srb sre sro srr srs ss- ssb sse sso ssr sss