⊦ j > 0 → i < i + j
0 < i, j < i, 0 < j, 0 < i1, 1 < i, i1 < i + i1, i1 > 0 → i < i + i1 ⊦ j < i + i1, j < i ∧ i < i + i1
Used terms: i1, i