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
    n = len(A)
    for i in range(1,n):
        B = A[1:i] + A[i+1:]
        yield (A[0] ^ A[i]) + max(gen_powers(B))

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