import sys
sys.setrecursionlimit(10**6)

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

def dfs(Used, curr):
    Used = list(Used)
    if min(Used) == 1:
        return curr
    ans = 0
    for i in range(n):
        if Used[i] == 0:
            for j in range(i + 1, n):
                if Used[j] == 0:
                    Used[i] = 1
                    Used[j] = 1
                    ans = max(ans, dfs(tuple(Used), curr ^ (A[i] + A[j])))
                    Used[i] = 0
                    Used[j] = 0
            break
    return ans

Used = [0 for _ in range(n)]
print(dfs(Used, 0))