from itertools import combinations, permutations 

N = input()
A = sorted(map(int, raw_input().split()))
ans = 0

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