⊦ m ≤ n ↔ ¬ n < m
stutf(nσ), ⌜n⌝ + ⌜1⌝ < leninv(nσ), ¬ inv(nσ)[n] < inv(nσ)[n + 1] ⊦
Used terms: inv(nσ)[n], inv(nσ)[n + 1]