0 < i, j0 < i, 0 ≤ i1, 0 ≤ j0, i * i0 ≤ i1 * i + j0 ⊦ i0 ≤ i1
0 < i, j0 < i, 0 ≤ i1, 0 ≤ j0, i0 ≤ i1 ⊦ i * i0 ≤ i1 * i + j0