intros n p; case p.
intros q H; inversion H.
intros p' q; case q.
intros Hle H; inversion H.
intros q' Hle Hle2; exact (construct_correct2 n p' q').
Qed.

(* Specifications: *)
Theorem construct_correct3 :
forall n n' p q p' q' d : nat,
S p = S d * p' ->
S q = S d * q' ->
S p + S q <= S n ->
p' + q' <= S n' -> Qpositive_c (S p) (S q) (S n) = Qpositive_c p' q' (S n').