-er a-a a-c aaa aac aae aao aap aar aax ac- aca acc ace aco acp acr acx aea aec aee aeo aep aer aex aoa aoc aoe aoo aop aor aox ap- apa apc ape apo app apr apx ar- ara arc are aro arp arr arx ax- axa axe axo axp axr axx c-- caa cac cae cao cap car cax cca ccc cce cco ccp ccr ccx ce- cea cec cee ceo cep cer cex co- coa coc coe coo cop cor cox cpa cpc cpe cpo cpp cpr cpx cra crc cre cro crp crr crx cxc cxo cxp cxr cxx eaa eac eae eao eap ear eax ec- eca ecc ece eco ecr ecx eea eec eee eeo eep eer eex eo- eoa eoc eoe eoo eop eor ep- epa epc epe epo epp epr epx era erc ere ero erp err ex- exa exc exe exo exp exr exx oaa oac oae oao oap oar oax oc- oca occ oco ocp ocr ocx oea oec oee oeo oep oer oex oo- ooa ooc ooo oop oor oox op- opa opc ope opo opp opr opx or- ora orc ore oro orp orr orx ox- oxa oxc oxo oxx p-p paa pac pae pao pap par pax pca pcc pce pco pcp pcr pcx pea pec pee peo pep per pex poa poc poe poo pop por pox ppa ppc ppe ppo ppp ppr ppx pra prc pre pro prp prr prx pxc pxe pxr ra- raa rac rae rao rap rar rax rca rcc rce rco rcp rcr rcx re- rea rec ree reo rep rer rex roa roc roe roo rop ror rox rpa rpc rpe rpo rpp rpr rpx rra rrc rrp rrr rxp rxr xaa xac xap xar xcp xcr xcx xee xep xer xex xoa xoc xoo xop xor xox xpa xpc xpe xpo xpp xrc xrx xxo xxp xxx