def search(x):
    j = 0
    for i in range(N):
        if NU[i] == True:
            if j == x:
                return i
            j += 1

def dfs(x):
    global ans, sum0
    if x == 0:
        ans = max(ans, sum0)
        return
    a = NU.index(True)
    NU[a] = False
    for b in range(a + 1,N):
        if True not in NU[b:]:
            continue
        c = NU[b:].index(True) + b
        NU[c] = False
        sum0 += A[a] ^ A[c]
        dfs(x - 1)
        sum0 -= A[a] ^ A[c]
        NU[c] = True
    NU[a] = True

N = int(input())
A = list(map(int, input().split()))
NU = [True] * N
ans = 0
sum0 = 0
dfs(N//2)
print(ans)