from itertools import combinations, permutations 

N = input()
A = sorted(map(int, raw_input().split()))
ans = 0
X = [0 for _ in xrange(N/2)]
Y = [0 for _ in xrange(N/2)]

for c in combinations(range(N), N/2):
    x, y = 0, 0
    for i in xrange(N):
        if i in c:
            X[x] = A[i]
            x += 1
        else:
            Y[y] = A[i]
            y += 1
    for p in permutations(X):
        tmp = 0
        for i in xrange(N/2):
            tmp ^= p[i] + Y[i]
        ans = max(ans, tmp)
        
print ans