def dfs(S):
    if S==(1<<N)-1:
        return [0]

    x=0
    while S&(1<<x):
        x+=1

    F=[]
    T=S|(1<<x)
    for y in range(x+1,N):
        if T&(1<<y):
            continue
        B=dfs(T|(1<<y))

        for b in B:
            F.append((A[x]+A[y])^b)
    return F

N=int(input())
A=list(map(int,input().split()))
print(max(dfs(0)))