j % 2 = 0, abs(i) ≤ j, i ≤ 0 ⊦ (i + j) / 2 = (i - 1) / 2 + j / 2
Used simplifier rules: forward-le-04: ⊦ j ≤ i ∧ i ≤ 0 → j ≤ 0; (forward) from specification int-abs