func main()
	var n: int :: cui@inputInt()
	var a: []int :: #[n]int
	for i(0, n - 1)
		do a[i] :: cui@inputInt()
	end for
	
	var ans: int :: 0
	for i(0, n - 1)
		for j(i + 1, n - 1)
			do ans :: lib@max(ans, a[i] $ bit64.xor(a[j] $ bit64) $ int)
		end for
	end for
	
	do cui@print("\{ans}\n")
end func