import scala.io.Source

object Main extends App {
  val inputStrings = Source.stdin.getLines().toList
  val Array(a, b, c, d) = inputStrings.head.split(' ').take(4).map(_.toInt)
  val x = (a + d - 1) / d
  val y = (c + b - 1) / b
  val result = if (x >= y) "Yes" else "No"
  print(result)
}
