import Control.Applicative
import Data.Bool (bool)

main :: IO ()
main = solve <$> f >>= putStrLn
  where
    f = map read <$> words <$> getLine

solve :: [Int] -> String
solve [a, b, c, d] = bool "No" "Yes" $ f a d >= f c b
  where
    f x y = (x + y - 1) `div` y
