-er a-a a-c aaa aac aae aap aar aas aax ac- aca acc ace acp acr acs acx aea aec aee aep aer aes aex ap- apa apc ape app apr aps apx ar- ara arc are arp arr ars arx as- asa asc ase asp asr ass asx ax- axa axe axp axr axs axx c-- caa cac cae cap car cas cax cca ccc cce ccp ccr ccs ccx ce- cea cec cee cep cer ces cex cpa cpc cpe cpp cpr cps cpx cra crc cre crp crr crs crx csa csc cse csp csr css csx cxc cxp cxr cxs cxx eaa eac eae eap ear eas eax ec- eca ecc ece ecr ecs ecx eea eec eee eep eer ees eex ep- epa epc epe epp epr eps epx era erc ere erp err ers es- esa esc ese esp esr ess esx ex- exa exc exe exp exr exs exx p-p paa pac pae pap par pas pax pca pcc pce pcp pcr pcs pcx pea pec pee pep per pes pex ppa ppc ppe ppp ppr pps ppx pra prc pre prp prr prs prx ps- psa psc pse psp psr pss psx pxc pxe pxr pxs ra- raa rac rae rap rar ras rax rca rcc rce rcp rcr rcs rcx re- rea rec ree rep rer res rex rpa rpc rpe rpp rpr rps rpx rra rrc rrp rrr rrs rsa rsc rse rsp rsr rss rsx rxp rxr rxs saa sac sae sap sar sas sax sca scc sce scp scr scs scx se- sea sec see sep ser ses sex spa spc spe spp spr sps spx sr- sra src sre srp srr srs srx ss- ssa ssc sse ssp ssr sss ssx sxc sxs xaa xac xap xar xas xcp xcr xcx xee xep xer xes xex xpa xpc xpe xpp xps xrc xrx xsa xsc xsp xss xxp xxx