| (i0 * j + j0) + j = (i0 + 1) * j + j0, (i0 * j + j0) + j < 0, j0 < j, j0 < 0, i0 < j + j0, i0 < j, 0 < j, 0 < j + j0, i0 < 0 ⊦ j0 + j = ((i0 * j + j0) + j) |%| j |
(i0 + 1) * j + j0 < 0, j0 < j, j0 < 0, i0 < j + j0, i0 < j, 0 < j, 0 < j + j0, i0 < 0 ⊦ j0 + j = ((i0 + 1) * j + j0) |%| j