(SIG
   (b   -> o)
   (f   o -> o)
   (c   -> o)
   (a   -> o)
   (h   o o -> o)
)
(RULES
   b -> f(b)
   c -> b
   f(f(f(c))) -> a
   f(h(b,b)) -> h(h(c,a),b)
)