-er b-p bbb bbe bbk bbo bbp bbr bbt bbx be- beb bee bek beo bep ber bet bex bkb bke bkk bko bkp bkr bkt bkx bob boe bok boo bop bor bot box bpb bpe bpo bpp bpr bpt bpx brb bre brk bro brp brr brt brx btb bte btk bto btp btr btt btx bxb bxo bxx ebb ebe ebk ebo ebp ebr ebt ebx eeb eee eek eeo eep eer eet eex ekb eke eko ekp ekr ekt eo- eob eoe eok eoo eop eor eot ep- epb epe epo epp epr ept epx erb ere erk ero erp err ert etb ete etk eto etp etr ett etx ex- exe exo exp exr ext exx k-t kbb kbe kbk kbo kbp kbr kbx ke- keb kee kek keo kep ker ket kex kkb kke kkk kkp kkr kkt kob koe kok koo kop kor kot kpe kpk kpo kpp kpr kpt krk kro krp krr krt ktb kte ktk kto ktp ktr ktt kxo ob- obb obe obk obo obp obr obt obx oeb oee oeo oep oer oet oex okb oke okk oko okp okr oo- oob ook ooo oop oor oot oox op- opb ope opk opo opp opr opt opx or- orb ore ork oro orp orr ort orx ot- otb ote otk oto otp otr ott ox- oxb oxo oxt oxx p-p pbb pbe pbk pbo pbp pbr pbt pbx peb pee pek peo pep per pet pex pkb pke pko pkp pkr pkt pob poe pok poo pop por pot pox ppb ppe ppk ppo ppp ppr ppt ppx prb pre prk pro prp prr prt prx pt- ptb pte ptk pto ptp ptr ptt ptx pxe pxk pxr pxt rbb rbe rbk rbo rbp rbr rbt rbx re- reb ree rek reo rep rer ret rex rkb rke rkk rko rkp rkt rob roe rok roo rop ror rot rox rpb rpe rpk rpo rpp rpr rpt rpx rrb rrk rrp rrr rrt rtb rte rtk rto rtp rtr rtt rtx rxp rxr t-x tbb tbe tbk tbo tbp tbr tbt te- teb tee tek teo tep ter tet tex tkb tke tkk tko tkp tkr tkt to- tob toe tok too top tor tot tox tpb tpe tpk tpo tpp tpr tpt tpx trb tre trk tro trp trr trt trx ttb tte ttk tto ttp ttr ttt ttx txe txk txt xbe xbr xbx xee xep xer xet xex xkb xke xok xoo xop xor xot xox xpb xpe xpo xpp xpt xrt xrx xtp xtr xtx xxo xxp xxx