(VAR X) (RULES f(f(a)) -> c(n__f(n__g(n__f(n__a)))) f(X) -> n__f(X) g(X) -> n__g(X) a -> n__a activate(n__f(X)) -> f(activate(X)) activate(n__g(X)) -> g(activate(X)) activate(n__a) -> a activate(X) -> X )