func main()
	var n: int :: cui@inputInt()
	var ans: int :: -1
	for i(n - 100, n + 100)
		if(i <= 0)
			skip i
		end if
		if(f(i).xor(i $ bit64) = n $ bit64)
			do ans :: i
			break i
		end if
	end for
	do cui@print("\{ans}\n")
	
	func f(n: int): bit64
		var res: int :: 0
		while(n <> 0)
			if(n % 2 = 1)
				do res :+ 1
			end if
			do n :/ 2
		end while
		ret res $ bit64
	end func
end func