route :: [Int] -> [Int] -> Int -> Int -> Int
route a1 a2 x n = sum $ b1 ++ b2
    where b1 = take x a1
          b2 = take (n - x + 1) $ reverse a2

main = do
    n <- readLn :: IO Int
    a1 <- map read . words <$> getLine :: IO [Int]
    a2 <- map read . words <$> getLine :: IO [Int]
    print $ maximum [ route a1 a2 x n | x <- [1..n]]