| ints1 ≠ [], perm(ints1, ints0 -1l i), i ∈ ints0, ∀ ints0. perm(ints1, ints0) → max(ints1) = max(ints0) ⊦ max(i, max(ints1)) = max(ints0) |
i ∈ ints0, perm(ints1, ints0 -1l i), ∀ ints0. perm(ints1, ints0) → max(ints1) = max(ints0) ⊦ ints1 = [], max(i, max(ints1)) = max(ints0)