-er b-p bbb bbe bbo bbp bbr bbs be- beb bee beo bep ber bes bob boe boo bop bor bos bpb bpe bpo bpp bpr bps brb bre bro brp brr brs bsb bse bso bsp bsr bss ebb ebe ebo ebp ebr ebs eeb eee eeo eep eer ees eo- eob eoe eoo eop eor eos ep- epb epe epo epp epr eps erb ere ero erp err ers es- esb ese eso esp esr ess ob- obb obe obo obp obr obs oeb oee oeo oep oer oes oo- oob ooo oop oor oos op- opb ope opo opp opr ops or- orb ore oro orp orr ors os- osb ose oso osp osr oss p-p pbb pbe pbo pbp pbr pbs peb pee peo pep per pes pob poe poo pop por pos ppb ppe ppo ppp ppr pps prb pre pro prp prr prs ps- psb pse pso psp psr pss rbb rbe rbo rbp rbr rbs re- reb ree reo rep rer res rob roe roo rop ror ros rpb rpe rpo rpp rpr rps rrb rrp rrr rrs rsb rse rso rsp rsr rss sbb sbe sbo sbp sbr sbs se- seb see seo sep ser ses sob soe soo sop sor sos spb spe spo spp spr sps sr- srb sre sro srp srr srs ss- ssb sse sso ssp ssr sss