⊦ i + j = j + i
j0 < j, 0 < j, 0 ≤ j0, 0 ≤ i0 ⊦ j = 0, i0 = 2 * i0 / 2 + (i0 * j + j0 < j * (1 + 2 * i0 / 2) ⊃ 0;1)
Used terms: 1, 2 * i0 / 2