Used simplifier rules: psh-03: ⊦ m ≠ 0 → (m -1 = n ↔ m = n +1);%psh-09: m ≠ 0 ⊦ m -1 < n ↔ m < n +1;%succ: ⊦ m +1 = m + 1;%a: ⊦ (m + n0) + n1 = m + n0 + n1;