-er a-a a-c aaa aac aae aar aas aax ac- aca acc ace acr acs acx aea aec aee aer aes aex ar- ara arc are arr ars arx as- asa asc ase asr ass asx ax- axa axe axr axs axx c-- caa cac cae car cas cax cca ccc cce ccr ccs ccx ce- cea cec cee cer ces cex cra crc cre crr crs crx csa csc cse csr css csx cxc cxr cxs cxx eaa eac eae ear eas eax ec- eca ecc ece ecr ecs ecx eea eec eee eer ees eex era erc ere err ers es- esa esc ese esr ess esx ex- exa exc exe exr exs exx ra- raa rac rae rar ras rax rca rcc rce rcr rcs rcx re- rea rec ree rer res rex rra rrc rrr rrs rsa rsc rse rsr rss rsx rxr rxs saa sac sae sar sas sax sca scc sce scr scs scx se- sea sec see ser ses sex sr- sra src sre srr srs srx ss- ssa ssc sse ssr sss ssx sxc sxs xaa xac xar xas xcr xcx xee xer xes xex xrc xrx xsa xsc xss xxx