n < n0, n ≤ m ⊦ n = min(min(m, n), n0)
Used simplifier rules: Min-left: ⊦ m < n → min(m, n) = m;% ⊦ m < n → n ≠ 0; (s)%f: ⊦ m < n → n ≠ 0; (forward) from specification nat-basic