-er b-p bbb bbe bbk bbo bbp bbr bbx be- beb bee bek beo bep ber bex bkb bke bkk bko bkp bkr bkx bob boe bok boo bop bor box bpb bpe bpo bpp bpr bpx brb bre brk bro brp brr brx bxb bxo bxx ebb ebe ebk ebo ebp ebr ebx eeb eee eek eeo eep eer eex ekb eke eko ekp ekr eo- eob eoe eok eoo eop eor ep- epb epe epo epp epr epx erb ere erk ero erp err ex- exe exo exp exr exx kbb kbe kbk kbo kbp kbr kbx ke- keb kee kek keo kep ker kex kkb kke kkk kkp kkr kob koe kok koo kop kor kpe kpk kpo kpp kpr krk kro krp krr kxo ob- obb obe obk obo obp obr obx oeb oee oeo oep oer oex okb oke okk oko okp okr oo- oob ook ooo oop oor oox op- opb ope opk opo opp opr opx or- orb ore ork oro orp orr orx ox- oxb oxo oxx p-p pbb pbe pbk pbo pbp pbr pbx peb pee pek peo pep per pex pkb pke pko pkp pkr pob poe pok poo pop por pox ppb ppe ppk ppo ppp ppr ppx prb pre prk pro prp prr prx pxe pxk pxr rbb rbe rbk rbo rbp rbr rbx re- reb ree rek reo rep rer rex rkb rke rkk rko rkp rob roe rok roo rop ror rox rpb rpe rpk rpo rpp rpr rpx rrb rrk rrp rrr rxp rxr xbe xbr xbx xee xep xer xex xkb xke xok xoo xop xor xox xpb xpe xpo xpp xrx xxo xxp xxx