proposition: Lemma Zp_addC : commutative Zp_add.
proof: Proof. by move=> x y; apply: val_inj; rewrite /= addnC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool choice eqtype ssrnat seq div) mathcomp(fintype bigop finset prime fingroup) mathcomp(ssralg finalg countalg)