-er b-p bbb bbc bbe bbo bbp bbr bcb bcc bce bco bcp bcr be- beb bec bee beo bep ber bob boc boe boo bop bor bpb bpc bpe bpo bpp bpr brb bre bro brp brr c-- cbb cbc cbe cbo cbp cbr ccb ccc cce cco ccp ccr ce- ceb cec cee ceo cep cer co- cob coc coe coo cop cor cpb cpc cpe cpo cpp cpr crb crc cre cro crp crr ebb ebc ebe ebo ebp ebr ec- ecb ecc ece eco ecr eeb eec eee eeo eep eer eo- eob eoc eoe eoo eop eor ep- epb epc epe epo epp epr erb erc ere ero erp err ob- obb obc obe obo obp obr oc- ocb occ oco ocp ocr oeb oec oee oeo oep oer oo- oob ooc ooo oop oor op- opb opc ope opo opp opr or- orb orc ore oro orp orr p-p pbb pbc pbe pbo pbp pbr pcb pcc pce pco pcp pcr peb pec pee peo pep per pob poc poe poo pop por ppb ppc ppe ppo ppp ppr prb prc pre pro prp prr rbb rbc rbe rbo rbp rbr rcb rcc rce rco rcp rcr re- reb rec ree reo rep rer rob roc roe roo rop ror rpb rpc rpe rpo rpp rpr rrb rrc rrp rrr