Require Import Arith.
Require Import ZArith.
Require Import Bool.

Open Scope nat_scope.

Check (plus 3).
Check (Zmult (-5)).
Check (Zabs_nat).
Check (5+Zabs_nat (5-19)).

(*Check (mult 3 (-45)%Z).*) (*Error: The term "(-45)%Z" has type "Z" while it is expected to have type "nat"*)