main :: IO ()
main = do
  [a, b, c, d] <- map (read :: String -> Int) . words <$> getLine
  putStrLn $ solver a b c d
  
solver :: Int -> Int -> Int -> Int -> String
solver a b c d 
  | c <= 0 = "Yes"
  | a <= 0 = "No"
  | otherwise = solver (a - d) b (c - b) d
