import qualified Data.Text as T
import qualified Data.Text.IO as T
import qualified Data.Text.Read as T

main :: IO ()
main = do
  [a, b, c, d] <- map unsafeTextToInt . T.words <$> T.getLine :: IO [Int]
  let
    m = pred c `div` b
    n = pred a `div` d
  putStrLn $ if m <= n then "Yes" else "No"

unsafeTextToInt :: T.Text -> Int
unsafeTextToInt s = case T.signed T.decimal s of
  Right (n, _) -> n
