⊦ Poton(n)(s) ↔ (∀ m. m ≤ n → Po(m)(s))
∀ m. m ≤ n0 → Ry(m)(s, s0), ∀ m. m ≤ n0 → Po(m)(s) ⊦ ∀ m. m ≤ n0 → Po(m)(s0)
Used terms: s0, n0