-er c-- ccc cce cck cco ccp ccr ccx ce- cec cee cek ceo cep cer cex ckc cko ckx co- coc coe cok coo cop cor cox cpc cpe cpk cpo cpp cpr cpx crc cre crk cro crp crr crx cxc cxk cxo cxp cxr cxx ec- ecc ece eck eco ecr ecx eec eee eek eeo eep eer eex ekc eke eko ekp ekr eo- eoc eoe eok eoo eop eor ep- epc epe epo epp epr epx erc ere erk ero erp err ex- exc exe exo exp exr exx kcc kce kck kcp kcr kcx ke- kec kee kek keo kep ker kex kkc kke kkk kkp kkr koc koe kok koo kop kor kpc kpe kpk kpo kpp kpr krc krk kro krp krr kxo oc- occ ock oco ocp ocr ocx oec oee oeo oep oer oex okc oke okk oko okp okr oo- ooc ook ooo oop oor oox op- opc ope opk opo opp opr opx or- orc ore ork oro orp orr orx ox- oxc oxo oxx p-p pcc pce pck pco pcp pcr pcx pec pee pek peo pep per pex pkc pke pko pkp pkr poc poe pok poo pop por pox ppc ppe ppk ppo ppp ppr ppx prc pre prk pro prp prr prx pxc pxe pxk pxr rcc rce rco rcp rcr rcx re- rec ree rek reo rep rer rex rkc rke rkk rko rkp roc roe rok roo rop ror rox rpc rpe rpk rpo rpp rpr rpx rrc rrk rrp rrr rxp rxr xcp xcr xcx xee xep xer xex xke xoc xok xoo xop xor xox xpc xpe xpo xpp xrc xrx xxo xxp xxx