-er b-p bbb bbe bbo bbp bbr bbx be- beb bee beo bep ber bex bob boe boo bop bor box bpb bpe bpo bpp bpr bpx brb bre bro brp brr brx bxb bxo bxx ebb ebe ebo ebp ebr ebx eeb eee eeo eep eer eex eo- eob eoe eoo eop eor ep- epb epe epo epp epr epx erb ere ero erp err ex- exe exo exp exr exx ob- obb obe obo obp obr obx oeb oee oeo oep oer oex oo- oob ooo oop oor oox op- opb ope opo opp opr opx or- orb ore oro orp orr orx ox- oxb oxo oxx p-p pbb pbe pbo pbp pbr pbx peb pee peo pep per pex pob poe poo pop por pox ppb ppe ppo ppp ppr ppx prb pre pro prp prr prx pxe pxr rbb rbe rbo rbp rbr rbx re- reb ree reo rep rer rex rob roe roo rop ror rox rpb rpe rpo rpp rpr rpx rrb rrp rrr rxp rxr xbe xbr xbx xee xep xer xex xoo xop xor xox xpb xpe xpo xpp xrx xxo xxp xxx