m + 1 < n, n ≤ n0, ∀ n0. n0 ∈ ns → n0 < n, n0 = m ∨ n0 ∈ ns ⊦
m + 1 ≤ n0, ∀ n0. n0 ∈ ns → n0 < n, n0 = m ∨ n0 ∈ ns ⊦ m + 1 < n