intros a b c d H H1; rewrite H; rewrite H1; auto.
Qed.

Theorem Qpositive_c_equiv :
forall n p q n' p' q' : nat,
S p + S q <= n ->
S p' + S q' <= n' ->
Qpositive_c (S p) (S q) n = Qpositive_c (S p') (S q') n' ->
S p * S q' = S p' * S q.