sushi :: Bool -> [Int] -> [[Int]]
sushi _ [] = [[]]
sushi took (x:xs)
	| took = sushi False xs
	| otherwise = map (x:) (sushi True xs) ++ (sushi False xs)

main = do
	getLine
	n <- getLine >>= return . map (read::String->Int) . words
	print $ maximum $ map sum $ sushi False n