proposition: Lemma Fp_Zcast : Zp_trunc (pdiv p) = Zp_trunc p.
proof: Proof. by rewrite /pdiv primes_prime. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool choice eqtype ssrnat seq div) mathcomp(fintype bigop finset prime fingroup) mathcomp(ssralg finalg countalg)