MAYBE
MAYBE
TRS:
 {
       a__f(X) -> f(X),
  a__f(f(a())) -> c(f(g(f(a())))),
    mark(c(X)) -> c(X),
    mark(f(X)) -> a__f(mark(X)),
    mark(g(X)) -> g(mark(X)),
     mark(a()) -> a()
 }
 Fail