# ar ≤ n, ∀ n. n ∈ nx1 → n < # ar, ∀ n. n ∈ nx0 → n < # ar, n ∈ nx0 ∨ n ∈ nx1 ⊦
Used simplifier rules: ⊦ m < n ↔ ¬ n ≤ m; (ss)