n = int(input())
if n >= 16:
    print((1 << 16) - 1)
    exit()

A = list(map(int, input().split()))
A.sort()
header = 1 << 15
DP = [[0 for _ in range(16)] for _ in range(n + 1)]
for i in range(n):
    a = A[i]
    for j in range(16):
        for k in range(16):
            DP[i + 1][k] = max(DP[i + 1][k], DP[i][j] | a)
            a, r = divmod(a, 2)
            a |= r * header
print(max(DP[n]))