-er b-p bbb bbc bbe bbo bbp bbr bbt bcb bcc bce bco bcp bcr bct be- beb bec bee beo bep ber bet bob boc boe boo bop bor bot bpb bpc bpe bpo bpp bpr bpt brb bre bro brp brr brt btb btc bte bto btp btr btt c-- cbb cbc cbe cbo cbp cbr cbt ccb ccc cce cco ccp ccr cct ce- ceb cec cee ceo cep cer cet co- cob coc coe coo cop cor cot cpb cpc cpe cpo cpp cpr cpt crb crc cre cro crp crr crt ctb ctc cte cto ctp ctr ctt ebb ebc ebe ebo ebp ebr ebt ec- ecb ecc ece eco ecr ect eeb eec eee eeo eep eer eet eo- eob eoc eoe eoo eop eor eot ep- epb epc epe epo epp epr ept erb erc ere ero erp err ert etb etc ete eto etp etr ett ob- obb obc obe obo obp obr obt oc- ocb occ oco ocp ocr oct oeb oec oee oeo oep oer oet oo- oob ooc ooo oop oor oot op- opb opc ope opo opp opr opt or- orb orc ore oro orp orr ort ot- otb otc ote oto otp otr ott p-p pbb pbc pbe pbo pbp pbr pbt pcb pcc pce pco pcp pcr pct peb pec pee peo pep per pet pob poc poe poo pop por pot ppb ppc ppe ppo ppp ppr ppt prb prc pre pro prp prr prt pt- ptb ptc pte pto ptp ptr ptt rbb rbc rbe rbo rbp rbr rbt rcb rcc rce rco rcp rcr rct re- reb rec ree reo rep rer ret rob roc roe roo rop ror rot rpb rpc rpe rpo rpp rpr rpt rrb rrc rrp rrr rrt rtb rtc rte rto rtp rtr rtt tbb tbc tbe tbo tbp tbr tbt tcb tcc tce tco tcp tcr tct te- teb tec tee teo tep ter tet to- tob toc toe too top tor tot tpb tpc tpe tpo tpp tpr tpt trb trc tre tro trp trr trt ttb ttc tte tto ttp ttr ttt