-er a-a a-c aaa aac aae aap aar ac- aca acc ace acp acr aea aec aee aep aer ap- apa apc ape app apr ar- ara arc are arp arr c-- caa cac cae cap car cca ccc cce ccp ccr ce- cea cec cee cep cer cpa cpc cpe cpp cpr cra crc cre crp crr eaa eac eae eap ear ec- eca ecc ece ecr eea eec eee eep eer ep- epa epc epe epp epr era erc ere erp err p-p paa pac pae pap par pca pcc pce pcp pcr pea pec pee pep per ppa ppc ppe ppp ppr pra prc pre prp prr ra- raa rac rae rap rar rca rcc rce rcp rcr re- rea rec ree rep rer rpa rpc rpe rpp rpr rra rrc rrp rrr