import fractions
from itertools import product
from collections import defaultdict
from collections import deque
inf = 1 << 60


def sgn(x):
    if x > 0:
        return 1
    elif x == 0:
        return 0
    else:
        return -1


def popC(x):
    ans = 0
    while x != 0:
        ans += x % 2
        x //= 2
    return ans


def LI():
    return list(map(int, input().split()))


def II():
    return int(input())


def SI():
    return input()


def f(x, y):
    ans = 0
    for i in range(60):
        bx = 0 if (x & (1 << i)) == 0 else 1
        by = 0 if (y & (1 << i)) == 0 else 1
        if i % 2:
            ans += (1 << i)*(bx | by)
        else:
            ans += (1 << i)*(bx & by)
    return ans

n = II()
a  =LI()
b = [0 for _ in range(1<<15)]
mask = 0b0101010101010101010101010101010101010101
for x in a:
    t = x&mask
    s = bin(t)[2:].zfill(30)
    s2 = []
    for i in range(15):
        s2.append(s[i*2+1])
    s2 = int("".join(s2),base=2)
    b[s2] |= x
mx = -1
for i in range((1<<15)-1,-1,-1):
    if b[i] != 0:
        if mx==-1:
            mx = b[i]
        else:
            mx = max(mx,f(mx,b[i]))
print(mx)