{-# LANGUAGE TypeApplications #-}

getIntList = map (read @Double) . words <$> getLine

main :: IO ()
main = do
  [a, b, c, d] <- getIntList
  let n1 = ceiling (c / b)
  let n2 = ceiling (a / d)
  putStrLn $ if n1 > n2 then "No" else "Yes"
