import Control.Monad
import Data.Maybe
import Data.List
import qualified Data.ByteString.Char8 as BS

main = abc164b

abc164b = do
    [a,b,c,d] <- getIntList
    putStrLn $ let aoki = divMod c a
                   taka = divMod a d
                in if fst aoki + (if snd aoki > 0 then 1 else 0) > fst taka + (if snd taka > 0 then 1 else 0)
                   then "No"
                   else "Yes"

readInt = fst . fromJust . BS.readInteger
readIntList = map readInt . BS.words
getIntList = readIntList <$> BS.getLine