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