N = int(input())
A = list(map(int, input().split()))

INF = 1<<60

dp = [-INF]*(1<<15)
for a in A:
    even, odd = 0, 0
    for i in range(30):
        if i%2 == 0:
            even |= (a>>i & 1)<<(i//2)
        else:
            odd |= (a>>i & 1)<<(i//2)
    if dp[even] == -INF: dp[even] = 0
    dp[even] |= odd
for bit in reversed(range(1<<15)):
    if dp[bit] == -INF: continue
    for i in range(15):
        if 1<<i & bit:
            if dp[bit^1<<i] == -INF: dp[bit^1<<i] = 0
            dp[bit^1<<i] |= dp[bit]

ans = 0
for bit in range(1<<15):
    if dp[bit] == -INF: continue
    SUM = 0
    for i in range(15):
        SUM |= (bit>>i & 1)<<(i*2)
        SUM |= (dp[bit]>>i & 1)<<(i*2+1)
    ans = max(ans, SUM)

print(ans)