import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N,*A = map(int, read().split())

def gen_powers(A):
    if not A:
        yield 0
        return
    for i, x in enumerate(A):
        if not i:
            continue
        pair_power = A[0] + x
        B = A[1:i] + A[i+1:]
        for p in gen_powers(B):
            yield p ^ pair_power

answer = max(gen_powers(A))
print(answer)