⊦ m ≤ n → dist(m, n) = n - m
¬ m + n ≤ m0 + n ⊦ dist(m + n, m0 + n) = dist(m, m0)
m + n ≤ m0 + n ⊦ m0 + n - m + n = dist(m, m0)
Used terms: m0 + n, m + n