fact: Definition Zis_gcd (a b d : Z) := (a = 0%Z -> b = 0%Z -> d = 0%Z) /\ (a <> 0%Z \/ b <> 0%Z -> (d > 0)%Z /\ Zdivides d a /\ Zdivides d b /\ (forall q : Z, Zdivides q a /\ Zdivides q b -> Zdivides q d)).
imports: CoRN.model.Zmod.ZDivides Coq.Init.Wf Coq(Lia)