0 ≤ i ∧ 0 < j → i = i0 * j + j0 ∧ 0 ≤ i0 ∧ 0 ≤ j0 ∧ j0 < j ⊦ j = 0, ∃ i0, j0. i = i0 * j + j0 ∧ abs(j0) < abs(j)