fact: Definition cubic_F: forall n, (forall y, y < n -> ({s : nat & {r : nat | y = (s * s) * s + r /\ r <= 3 * (s * s) + 3 * s}})) -> ({s : nat & {r : nat | n = (s * s) * s + r /\ r <= 3 * (s * s) + 3 * s}}).
imports: Arith ArithRing Lia Wf_nat