| nσ[m0] < nσ[m0 + 1], nσ[m0] < n, ⌜m0⌝ < # nσ, ⌜m0⌝ + ⌜1⌝ < # nσ, stutf(nσ), n ≤ nσ[m0 + 1], ⌜m0⌝ < # nσ ∧ stutf(nσ) ∧ m0 ≤ nσ[m0] → (∃ m1. m1 ≤ m0 ∧ nσ[m1] = m0) ⊦ ∃ m. m ≤ m0 + 1 ∧ nσ[m] = n |
⌜m0⌝ + ⌜1⌝ < # nσ, ⌜m0⌝ < # nσ, nσ[m0] < n, nσ[m0] < nσ[m0 + 1], stutf(nσ), n ≤ nσ[m0 + 1], m0 ≤ nσ[m0] → m ≤ nσ[m] ∧ nσ[m] = m0 ⊦ ∃ m. m ≤ m0 + 1 ∧ nσ[m] = n