import Control.Monad

main :: IO ()
main = do
  n <- readLn :: IO Int
  as <- replicateM 2 $ fmap (map read . words) getLine

  ans <- fmap maximum $ forM [0..n-1] $ \i -> do
    return $ sum $ take (i+1) (as !! 0) ++ drop i (as !! 1)

  print ans