proposition: Lemma groupX x n : x \in G -> x ^+ n \in G.
proof: Proof. by move=> Gx; elim: n => [|n IHn]; rewrite ?group1 // expgS groupM. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)