(count ((S n)*(S m)) f) = (count (S n) f1)*(count (S m) f2).
intros.unfold count.
rewrite < eq_map_iter_i_sigma.
-rewrite > (permut_to_eq_map_iter_i plus assoc_plus sym_plus ? ? ? (\lambda i.g (div i (S n)) (mod i (S n)))).
+rewrite > (permut_to_eq_map_iter_i plus assoc_plus sym_plus ? ? ?
+ (\lambda i.g (div i (S n)) (mod i (S n)))).
rewrite > eq_map_iter_i_sigma.
rewrite > eq_sigma_sigma1.
apply (trans_eq ? ?
sigma m (\lambda b.(bool_to_nat (f2 b))*(bool_to_nat (f1 a))) O) O)).
apply eq_sigma.intros.
apply eq_sigma.intros.
-rewrite > (div_mod_spec_to_eq (i1*(S n) + i) (S n) ((i1*(S n) + i)/(S n)) ((i1*(S n) + i) \mod (S n)) i1 i).
-rewrite > (div_mod_spec_to_eq2 (i1*(S n) + i) (S n) ((i1*(S n) + i)/(S n)) ((i1*(S n) + i) \mod (S n)) i1 i).
+rewrite > (div_mod_spec_to_eq (i1*(S n) + i) (S n) ((i1*(S n) + i)/(S n))
+ ((i1*(S n) + i) \mod (S n)) i1 i).
+rewrite > (div_mod_spec_to_eq2 (i1*(S n) + i) (S n) ((i1*(S n) + i)/(S n))
+ ((i1*(S n) + i) \mod (S n)) i1 i).
rewrite > H3.
apply bool_to_nat_andb.
simplify.apply le_S_S.assumption.