def anotherMinimaxProblem(a):
    if all(x == 0 for x in a): 
        return 0

    n = len(a)
    max_bit = max(a).bit_length()

    for bit in range(max_bit - 1, -1, -1):
        ones, zeros = [], []
        for num in a:
            if num & (1 << bit):
                ones.append(num)
            else:
                zeros.append(num)
        if zeros and ones:
            break

    if not zeros or not ones:
        return min(a[i] ^ a[j] for i in range(n) for j in range(i + 1, n))

    return min(x ^ y for x in zeros for y in ones)