proposition: Lemma prod_enumP : Finite.axiom prod_enum.
proof: Proof. by case=> x1 x2; rewrite (predX_prod_enum (pred1 x1) (pred1 x2)) !card1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(path div)