⊦ 0 ≤ i * j ↔ i = 0 ∨ j = 0 ∨ 0 < i ∧ 0 < j ∨ i < 0 ∧ j < 0
Used simplifier rules: lels-02: ⊦ i ≠ j → (i ≤ j ↔ i < j); from specification int-abs