func main()
	var n: int :: cui@inputInt()
	var a: int :: 0
	var b: int :: cui@inputInt()
	for(1, n - 1)
		var t: int :: a
		do a :: [a, b].max()
		do b :: t + cui@inputInt()
	end for
	var ans: int :: [a, b].max()
	do cui@print("\{ans}\n")
end func