proposition: Lemma card_mem_repr A : #|A| > 0 -> repr A \in A.
proof: Proof. by rewrite lt0n => /existsP[x]; apply: mem_repr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)