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