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

main :: IO ()
main = do
  solve <$> getl (readil B.readInt) >>= print

solve :: [Int] -> Double
solve [a, b, x, y] = if x * b <= a * y
                     then fromIntegral ((a + b) * x) / (fromIntegral a)
                     else fromIntegral ((a + b) * y) / (fromIntegral b)

getl :: (ByteString -> a) -> IO a
getl f = f <$> B.getLine

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