from functools import lru_cache

n = int(input())
a = list(map(int, input().split()))

@lru_cache(maxsize=None)
def dfs(mask):
    if mask == (1 << n) - 1:
        return 0
    # Find the first unpaired player
    for i in range(n):
        if not (mask & (1 << i)):
            first = i
            break
    max_total = 0
    # Pair the first with all possible others
    for j in range(first + 1, n):
        if not (mask & (1 << j)):
            new_mask = mask | (1 << first) | (1 << j)
            current_xor = a[first] ^ a[j]
            total = current_xor + dfs(new_mask)
            if total > max_total:
                max_total = total
    return max_total

print(dfs(0))