main = do
    n  <- readLn
    as <- map read . words <$> getLine
    bs <- map read . words <$> getLine
    print $ maximum [ sum $ zipWith3 z as bs [1 .. n] | z <- map zipper [1 .. n] ]

zipper k a b i | i < k     = a
               | i > k     = b
               | otherwise = a + b
