-er b-p bbb bbe bbo bbp bbr bbt be- beb bee beo bep ber bet bob boe boo bop bor bot bpb bpe bpo bpp bpr bpt brb bre bro brp brr brt btb bte bto btp btr btt ebb ebe ebo ebp ebr ebt eeb eee eeo eep eer eet eo- eob eoe eoo eop eor eot ep- epb epe epo epp epr ept erb ere ero erp err ert etb ete eto etp etr ett ob- obb obe obo obp obr obt oeb oee oeo oep oer oet oo- oob ooo oop oor oot op- opb ope opo opp opr opt or- orb ore oro orp orr ort ot- otb ote oto otp otr ott p-p pbb pbe pbo pbp pbr pbt peb pee peo pep per pet pob poe poo pop por pot ppb ppe ppo ppp ppr ppt prb pre pro prp prr prt pt- ptb pte pto ptp ptr ptt rbb rbe rbo rbp rbr rbt re- reb ree reo rep rer ret rob roe roo rop ror rot rpb rpe rpo rpp rpr rpt rrb rrp rrr rrt rtb rte rto rtp rtr rtt tbb tbe tbo tbp tbr tbt te- teb tee teo tep ter tet to- tob toe too top tor tot tpb tpe tpo tpp tpr tpt trb tre tro trp trr trt ttb tte tto ttp ttr ttt