proposition: Lemma BZprod_succ_r n m: intp n -> intp m -> n *z (BZsucc m) = (n *z m) +z n.
proof: Proof. by move => pa pb; rewrite /BZsucc (BZprodDr pa pb ZS1) BZprod_1r. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)