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Inductive divides : nat -> nat -> Prop :=
    dividesDef : forall a b q : nat, b = q * a -> divides a b.(******************************************************************************)
 
Inductive divides : nat -> nat -> Prop :=
    dividesDef : forall a b q : nat, b = q * a -> divides a b.

Lemma div_divides : forall x y : nat, (exists q : _, is_div x y q 0) -> divides y x.