# σ0 = # σ1, ⌜n⌝ < # σ1, ¬ # σ1 < ⌜n + 1⌝ → σ0 to n + 1 = σ1 to n + 1, ∀ n. ¬ # σ1 < ⌜n⌝ → σ0 to n = σ1 to n ⊦ σ0[n] = σ1[n]
Used terms: n + 1