n = int(input())
a = list(map(int, input().split()))

c = 0x55555555
def f(a):
    x = 0
    for v in a:
        x |= v ^ c
    return x ^ c

now = f(a)

for i in range(28, -2, -2):
    na = [x for x in a if x >> i & 1]
    if na:
        nxt = f(na)
        if nxt > now:
            now = nxt
            a = na
print(now)