LIMIT = 15

def f(x: int, y: int) -> int:
    res = 0
    for i in range(2 * LIMIT):
        xi = (x >> i) & 1
        yi = (y >> i) & 1

        if i % 2 == 0:
            res |= (xi & yi) << i
        else:
            res |= (xi | yi) << i

    return res

def even(n: int) -> int:
    res = 0
    for i in range(LIMIT):
        ni = (n >> (2 * i)) & 1
        res |= ni << i

    return res

N = int(input())
A = [int(s) for s in input().split()]

values = [0] * (1 << LIMIT)

for a in A:
    even_a = even(a)
    values[even_a] = max(a, f(values[even_a], a))

for bit in range((1 << LIMIT) - 1, -1, -1):
    for i in range(LIMIT):
        if (bit >> i) & 1 == 0:
            continue
        nbit = bit & ~(1 << i)
        values[nbit] = max(values[nbit], values[bit], f(values[nbit], values[bit]))

print(max(values))