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