object Main {
  def main(args: Array[String]): Unit = {
    import scala.io.StdIn.readLine
    val Array(tHP, tATK, aHP, aATK) = readLine.split(" ").map(_.toInt)

    val tTurn = (aHP / tATK) + (if (aHP % tATK != 0) 1 else 0)
    val aTurn = (tHP / aATK) + (if (tHP % aATK != 0) 1 else 0)

    val ans = (tTurn <= aTurn)
    println(if(ans) "Yes" else "No")
  }
}
