#[deprecated(since="8.17")]
Notation Zis_gcd_for_euclid := deprecated_Zis_gcd_for_euclid (only parsing).

Local Lemma extgcd_rec_helper r1 r2 q : Z.gcd r1 r2 = Z.gcd a b -> Z.gcd (r2 - q * r1) r1 = Z.gcd a b.