-er b-p bbb bbe bbo bbp bbr be- beb bee beo bep ber bob boe boo bop bor bpb bpe bpo bpp bpr brb bre bro brp brr ebb ebe ebo ebp ebr eeb eee eeo eep eer eo- eob eoe eoo eop eor ep- epb epe epo epp epr erb ere ero erp err ob- obb obe obo obp obr oeb oee oeo oep oer oo- oob ooo oop oor op- opb ope opo opp opr or- orb ore oro orp orr p-p pbb pbe pbo pbp pbr peb pee peo pep per pob poe poo pop por ppb ppe ppo ppp ppr prb pre pro prp prr rbb rbe rbo rbp rbr re- reb ree reo rep rer rob roe roo rop ror rpb rpe rpo rpp rpr rrb rrp rrr