proposition: Lemma mulUg A B C : (A :|: B) * C = (A * C) :|: (B * C).
proof: Proof. exact: imset2Ul. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)