N = int(input())
A = list(map(int,input().split()))
B = [0]*N
C = []
ans = 0
def dfs(n):
    global ans
    if n==N:
        cnt = 0
        for k in range(len(C)):
            cnt = cnt^C[k]
        ans = max(ans,cnt)
        return
    ind0 = B.index(0)
    for ind1 in range(ind0+1,N):
        if B[ind1]==0:
            C.append(A[ind0]+A[ind1])
            B[ind0] = 1
            B[ind1] = 1
            dfs(n+2)
            B[ind0] = 0
            B[ind1] = 0
            C.pop()
dfs(0)
print(ans)