func main()
	var N: int :: cui@input().toInt(&)
	var V: []int :: #[N]int
	var _: [][]char :: cui@input().split(" ")
	for i(0, N - 1)
		do V[i] :: _[i].toInt(&)
	end for
	var dp: []int :: #[2]int
	do dp[0] :: 0
	do dp[1] :: V[0]
	for i(1, N - 1)
		var dp0: int :: dp[0]
		var dp1: int :: dp[1]
		do dp[0] :: [dp0, dp1].max()
		do dp[1] :: dp0 + V[i]
	end for
	var ans: int :: [dp[0], dp[1]].max()
	do cui@print("\{ans}\n")
end func