myCeil :: Int -> Int -> Int
myCeil a b = (div a b) + c
 where c = if((mod a b) == 0) then 0 else 1

main :: IO ()
main = do
 [a,b,c,d] <- map read . words <$> getLine :: IO[Int]
 putStr $ (\a b c d -> if (myCeil c b) <= (myCeil a d) then "Yes" else "No") a b c d