Used simplifier rules: ⊦ i * j = j * i;% ⊦ i + j < j ↔ i < 0;% ⊦ i ≤ j → (¬ ¬ j < i ↔ false);% ⊦ i + j + i0 = (i + j) + i0;% ⊦ i + j = j + i;