N=int(input())
A=list(map(int,input().split()))

DP=[0]*(1<<N)

for i in range(1<<N):
    for j in range(N):
        if i & (1<<j) != 0:
            continue
        for k in range(N):
            if i & (1<<k) != 0:
                continue

            plus=A[j]^A[k]

            DP[i|(1<<j)|(1<<k)]=max(DP[i|(1<<j)|(1<<k)],DP[i]+plus)

print(DP[-1])