n = int(input())
A = list(map(int, input().split()))
used = [False] * n

def dfs(i, x):
    if 2 * i == n:
        return x
    
    for j in range(n):
        if not used[j]:
            used[j] = True
            a = A[j]
            break
    ret = 0
    for k in range(j + 1, n):
        if not used[k]:
            used[k] = True
            ret = max(ret, dfs(i + 1, x ^ (a + A[k])))
            used[k] = False
    used[j] = False
    return ret
    
print(dfs(0, 0))