gcd(m, n1) = 0, n1 ≤ m, ∀ n0, m0. n0 < n1 + m → gcd(m0, n0) = 0 ∧ m0 < n0 → false ⊦ n1 = 0, gcd(n1, m) = 0 ∧ n1 < m