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