Let f : [-1, 1] → R be defined as f(x) = ax2 + bx + c for all x ∈ [-1, 1], where a, b, c ∈ R such that f(–1) = 2, f'(–1) = 1 and for x ∈ (-1, 1) the maximum value of f"(x) is \(\frac{1}{2}\). If f(x) \(\leq\) α, x ∈ [–1, 1], then the least value of a is equal to ______.