def f(x, y):
    res = 0
    for i in range(max(x.bit_length(), y.bit_length())):
        xi = (x >> i) & 1
        yi = (y >> i) & 1
        if i % 2 == 0:
            res |= (xi & yi) << i
        else:
            res |= (xi | yi) << i
    return res


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

dp = A[0]

for i in range(1, N):
    dp = max(f(dp, A[i]), A[i])

print(dp)