m0 + n0 + n1 + n2 < m + n + m1, m ≤ m0, n ≤ n0, m1 ≤ n1 ⊦
Used simplifier rules: ⊦ m < n → n ≠ 0; (s)%f: ⊦ m < n → n ≠ 0; (forward) from specification nat-basic