import sys

sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


N = I()
A = LI()


def f(X):
    if not X:
        return [0]
    M = len(X)
    res = []
    for i in range(1,M):
        a = X[0]+X[i]
        Y = f(X[1:i]+X[i+1:])
        for y in Y:
            res.append(a^y)
    return res


print(max(f(A)))