proposition: Lemma mulgU A B C : A * (B :|: C) = (A * B) :|: (A * C).
proof: Proof. exact: imset2Ur. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)