proposition: Lemma card1_trivg : #|G| = 1%N -> G :=: 1.
proof: Proof. by move=> G1; rewrite card_le1_trivg ?G1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)