import Control.Monad

rInt :: String -> Int
rInt = read

solve (a1:a2:[]) (b1:b2:[]) (c:d:[]) = a' + b'
    where
        a'  | c == 0    = a1
            | otherwise = if (c - a2) <= 0 then a1 else a1 - (c - a2)
        b'  | d == 0    = 0
            | otherwise = if (b1 + c - a2) > d then d else b1 + c - a2

main = do
    [as, bs, cd] <- map (map rInt . words) <$> replicateM 3 getLine
    print $ solve as bs cd