| ¬ max(x1) < a, ∀ x0. x1 + x0 = [] ∨ max(x1 + x0) = max(x1) ∨ max(x1 + x0) = max(x0) ⊦ max(x1 + x0) = max(x1), x1 + x0 = [], max(x1 + x0) = max(x0), x1 = [], max(x1 + x0) < a |
∀ x0. x1 + x0 = [] ∨ max(x1 + x0) = max(x1) ∨ max(x1 + x0) = max(x0) ⊦ max(x1 + x0) = max(x1), x1 + x0 = [], max(x1 + x0) = max(x0), x1 = [], max(x1 + x0) < a, max(x1) < a