def solve(xs, ac)
  return ac if xs.size == 0
  ys = xs.clone
  y = ys[0]
  ys.delete_at 0
  ans = 0
  ys.size.times do |i|
    zs = ys.clone
    z = ys[i]
    zs.delete_at i
    ans = [ans, solve(zs, (y + z) ^ ac)].max
  end
  ans
end
_ = gets.to_i
xs = gets.split.map(&:to_i)
p solve(xs, 0)