import Control.Applicative ((<$>))
import Text.Printf (printf)

computeMax :: RealFloat a => a -> a -> a
computeMax c d
    | 3.5 * c <= 1.4 * d = f 0 $ 3.5 * c
    | 1 / 3 * c <= d && 1.4 * d < 3.5 * c = f xp yp
    | otherwise = f (4 * d) 0
    where
        f x y = 1000 * x + 2000 * y
        xp = 20 / 13 * c - 8 / 13 * d
        yp = -7 / 13 * c + 21 / 13 * d

main :: IO ()
main = do
    [c, d] <- fmap read . words <$> getLine :: IO [Double]
    printf "%.12f\n" (computeMax c d)