import qualified Data.Vector.Unboxed as VU
import qualified Data.ByteString.Char8 as B
import Data.Char

solve as bs n = VU.maximum $ VU.generate n $ \i -> VU.sum (VU.take (i+1) as) + VU.sum (VU.drop i bs)
main = do
    n <- readLn :: IO Int
    as <- VU.unfoldrN n (B.readInt . B.dropWhile isSpace) <$> B.getLine
    bs <- VU.unfoldrN n (B.readInt . B.dropWhile isSpace) <$> B.getLine
    print $ solve as bs n