(VAR X)
(RULES 
active(f(f(X))) -> mark(c(f(g(f(X)))))
active(c(X)) -> mark(d(X))
active(h(X)) -> mark(c(d(X)))
active(f(X)) -> f(active(X))
active(h(X)) -> h(active(X))
f(mark(X)) -> mark(f(X))
h(mark(X)) -> mark(h(X))
proper(f(X)) -> f(proper(X))
proper(c(X)) -> c(proper(X))
proper(g(X)) -> g(proper(X))
proper(d(X)) -> d(proper(X))
proper(h(X)) -> h(proper(X))
f(ok(X)) -> ok(f(X))
c(ok(X)) -> ok(c(X))
g(ok(X)) -> ok(g(X))
d(ok(X)) -> ok(d(X))
h(ok(X)) -> ok(h(X))
top(mark(X)) -> top(proper(X))
top(ok(X)) -> top(active(X))
)