-er a-a a-c aaa aac aae aap aar aax ac- aca acc ace acp acr acx aea aec aee aep aer aex ap- apa apc ape app apr apx ar- ara arc are arp arr arx ax- axa axe axp axr axx c-- caa cac cae cap car cax cca ccc cce ccp ccr ccx ce- cea cec cee cep cer cex cpa cpc cpe cpp cpr cpx cra crc cre crp crr crx cxc cxp cxr cxx eaa eac eae eap ear eax ec- eca ecc ece ecr ecx eea eec eee eep eer eex ep- epa epc epe epp epr epx era erc ere erp err ex- exa exc exe exp exr exx p-p paa pac pae pap par pax pca pcc pce pcp pcr pcx pea pec pee pep per pex ppa ppc ppe ppp ppr ppx pra prc pre prp prr prx pxc pxe pxr ra- raa rac rae rap rar rax rca rcc rce rcp rcr rcx re- rea rec ree rep rer rex rpa rpc rpe rpp rpr rpx rra rrc rrp rrr rxp rxr xaa xac xap xar xcp xcr xcx xee xep xer xex xpa xpc xpe xpp xrc xrx xxp xxx