⊦ Rton(n)(s, s0) ↔ (∀ m. m ≤ n → Ry(m)(s, s0))
⊦ (∀ m. m ≤ n0 → Ry(m)(s1, s2)) ∧ (∀ m. m ≤ n0 → Ry(m)(s2, s3)) → Rton(n0)(s1, s3)
Used terms: s2, s1, n0