-er a-a a-c aaa aac aae aao aap aar aas aax ac- aca acc ace aco acp acr acs acx aea aec aee aeo aep aer aes aex aoa aoc aoe aoo aop aor aos aox ap- apa apc ape apo app apr aps apx ar- ara arc are aro arp arr ars arx as- asa asc ase aso asp asr ass asx ax- axa axe axo axp axr axs axx c-- caa cac cae cao cap car cas cax cca ccc cce cco ccp ccr ccs ccx ce- cea cec cee ceo cep cer ces cex co- coa coc coe coo cop cor cos cox cpa cpc cpe cpo cpp cpr cps cpx cra crc cre cro crp crr crs crx csa csc cse cso csp csr css csx cxc cxo cxp cxr cxs cxx eaa eac eae eao eap ear eas eax ec- eca ecc ece eco ecr ecs ecx eea eec eee eeo eep eer ees eex eo- eoa eoc eoe eoo eop eor eos ep- epa epc epe epo epp epr eps epx era erc ere ero erp err ers es- esa esc ese eso esp esr ess esx ex- exa exc exe exo exp exr exs exx oaa oac oae oao oap oar oas oax oc- oca occ oco ocp ocr ocs ocx oea oec oee oeo oep oer oes oex oo- ooa ooc ooo oop oor oos oox op- opa opc ope opo opp opr ops opx or- ora orc ore oro orp orr ors orx os- osa osc ose oso osp osr oss osx ox- oxa oxc oxo oxx p-p paa pac pae pao pap par pas pax pca pcc pce pco pcp pcr pcs pcx pea pec pee peo pep per pes pex poa poc poe poo pop por pos pox ppa ppc ppe ppo ppp ppr pps ppx pra prc pre pro prp prr prs prx ps- psa psc pse pso psp psr pss psx pxc pxe pxr pxs ra- raa rac rae rao rap rar ras rax rca rcc rce rco rcp rcr rcs rcx re- rea rec ree reo rep rer res rex roa roc roe roo rop ror ros rox rpa rpc rpe rpo rpp rpr rps rpx rra rrc rrp rrr rrs rsa rsc rse rso rsp rsr rss rsx rxp rxr rxs saa sac sae sao sap sar sas sax sca scc sce sco scp scr scs scx se- sea sec see seo sep ser ses sex soa soc soe soo sop sor sos sox spa spc spe spo spp spr sps spx sr- sra src sre sro srp srr srs srx ss- ssa ssc sse sso ssp ssr sss ssx sxc sxs xaa xac xap xar xas xcp xcr xcx xee xep xer xes xex xoa xoc xoo xop xor xos xox xpa xpc xpe xpo xpp xps xrc xrx xsa xsc xsp xss xxo xxp xxx