N = gets.to_i
a = gets.split(" ").map{|s| s.to_i}

max = 0

s = 0
a.each {|x|
	s ^= x
}

s ^= s

0.upto(N-1) {|i|
	i.upto(N-1) {|j|
		x = s ^ a[i] ^ a[j]
		max = x if max < x
	}
}

puts max