import Control.Applicative ((<$>))
import Data.Char (isSpace)
import Data.List (unfoldr)
import Data.ByteString.Char8 (ByteString)
import qualified Data.ByteString.Char8 as B

getL :: (ByteString -> [Int]) -> IO [Int]
getL f = f <$> B.getContents

readIL :: (ByteString -> Maybe (Int, ByteString)) -> (ByteString -> [Int])
readIL f = unfoldr g
    where
        g s = do
            (n, s') <- f s
            return (n, B.dropWhile isSpace s')

main :: IO ()
main = print =<< solve <$> getL (readIL B.readInt)

solve :: [Int] -> Int
solve [aw, ab, bw, bb, c, d]
    | c <= ab && d >= bw            = aw + bw
    | c <= ab && d < bw             = aw + d
    | c > ab  && d >= (bw + c - ab) = aw + bw 
    | c > ab  && d < (bw + c - ab)  = (aw - (c - ab)) + d
    | otherwise                     = 0