⊦ m < n ↔ (∃ m0. m + m0 = n ∧ m0 ≠ 0)
∃ m0. 2^ n + m0 = 2^ m ∧ m0 ≠ 0, 2^ m ≤ 2^ n, n < m ⊦ n = m, m = 0
Used terms: 2^ m, 2^ n