n ≤ m ⊦ (m - n) + n = m
¬ i→n(i) ≤ i→n(j) + m, i ≤ j, 0 ≤ i, 0 ≤ j ⊦ (i→n(j) + m - i→n(i)) + i→n(i) = i→n(j) + m
Used terms: i→n(i), i→n(j) + m