i + i0 < j + j0, j0 < j1, i1 < i0 ⊦ i + i1 < j + j1
Used simplifier rules: ⊦ i < j → ¬ j < i; (s)% ⊦ ¬ i < j → (i = j ↔ ¬ j < i); (ss)