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