(VAR X)
(RULES 
a__f(f(X)) -> a__c(f(g(f(X))))
a__c(X) -> d(X)
a__h(X) -> a__c(d(X))
mark(f(X)) -> a__f(mark(X))
mark(c(X)) -> a__c(X)
mark(h(X)) -> a__h(mark(X))
mark(g(X)) -> g(X)
mark(d(X)) -> d(X)
a__f(X) -> f(X)
a__c(X) -> c(X)
a__h(X) -> h(X)
)