TIMEOUT
MAYBE
Trs:
 {       f(mark(X)) -> mark(f(X)),
           f(ok(X)) -> ok(f(X)),
           c(ok(X)) -> ok(c(X)),
         g(mark(X)) -> mark(g(X)),
           g(ok(X)) -> ok(g(X)),
        proper(a()) -> ok(a()),
       proper(f(X)) -> f(proper(X)),
       proper(c(X)) -> c(proper(X)),
       proper(g(X)) -> g(proper(X)),
  active(f(f(a()))) -> mark(c(f(g(f(a()))))),
       active(f(X)) -> f(active(X)),
       active(g(X)) -> g(active(X)),
       top(mark(X)) -> top(proper(X)),
         top(ok(X)) -> top(active(X))}
 Open