proposition: Lemma mulg_subl A B : 1 \in B -> A \subset A * B.
proof: Proof. by move=> B1; rewrite -{1}(mulg1 A) mulgS ?sub1set. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)