∀ (motive : ℕ → (x x_1 : ℕ) → x < x_1 → Prop) (x x_1 x_2 : ℕ) (x_3 : x_1 < x_2),
  (∀ (n₁ n₂ : ℕ) (h : n₁ < n₂), motive 0 n₁ n₂ h) →
    (∀ (m n : ℕ) (_h : 0 < n + 1), motive m.succ 0 n.succ _h) →
      (∀ (m n₁ n₂ : ℕ) (h : n₁ + 1 < n₂ + 1), motive m.succ n₁.succ n₂.succ h) → motive x x_1 x_2 x_3