max∞(λ n0. nσ[n0] = nσ[n]) = ∞, # nσ = ∞, stutf(nσ), nσ[n] ≤ nσ[m], ∞.n < n, ∀ m0. m < m0 → nσ[m0] = nσ[m] + 1 ⊦