| i * i0 + j0 = i1 * j + j1, j1 < j, j0 < j, i0 ≤ j, i < i1, 0 ≤ j1, 0 ≤ j0, 0 < j, 0 ≤ i0, 0 ≤ j, 0 ≤ i, 0 < i1 ⊦ i * i0 + j0 < i1 * j + j1 |
j1 < j, j0 < j, i0 ≤ j, i < i1, 0 ≤ j1, 0 ≤ j0, 0 < j, 0 ≤ i0, 0 ≤ j, 0 ≤ i, 0 < i1 ⊦ i * i0 + j0 < i1 * j + j1