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