main :: IO ()
main = do
  [vl, vr] <- map read . words <$> getLine
  d <- read <$> getLine
  w <- read <$> getLine
  print $ solve vl vr d w

solve :: Double -> Double -> Double -> Double -> Double
solve vl vr d w = d * w * s / (w + vr)
  where
    r1 = (w - vl) / (w + vl)
    r2 = (w - vr) / (w + vr)
    s = (1 + r1) / (1 - r1 * r2)