n = m + 1, # y = m, 1 ≤ n ⊦ n = 0, ∃ y0, z0. a ' + y + z = y0 + z0 ∧ # y0 = n
Used simplifier rules: n ≠ 0 ⊦ m = n - 1 ↔ n = m + 1; (elim) Used terms: n, m