intros. apply nsum_of_zeros. intro i.
apply has_n_elements_inj with (B:=V i)(C:=V i).
exact (V'a i). apply empty_then_has_zero_elements.
simpl. unfold eq_part. intro g. split.
intro H. apply in_part_comp_r with A. apply(Va i). exact H.
apply has_zero_elements_then_empty. unfold has_n_elements.
exists AH. split. exact AH'. exact AH''.
simpl. intuition. apply Refl. Qed.

(* Specifications: *)
Lemma incexc3:forall(n:Nat)(G:Setoid)(A:part_set G)
(AH:seq n A)(AH':full A =' seq_set AH)(AH'':distinct AH)
(c:Nat)(V:seq c(part_set G))
(Va:forall(i:fin c)(g:G),in_part g(V i)->in_part g A)
(Vb:forall(g:G)(H:in_part g A),exists i:fin c,in_part g(V i))
(Vc:forall(g:G)(H:in_part g A)(i i':fin c),
in_part g(V i)->in_part g(V i')->i =' i')
(V':seq c Nat)(V'a:forall(i:fin c),has_n_elements(V' i)(V i)),
nsum c V' =' n.