fun main(args: Array<String>) {
  val input1 = readLine()!!.split(" ").map(String::toInt)
  var lifeT = input1[0]
  var attT = input1[1]
  var lifeA = input1[2]
  var attA = input1[3]
  var isContinue = true
  var result = "No"
  while(isContinue) {
    lifeA -= attT
    isContinue = lifeA > 0
    if (!isContinue) {
      result = "Yes"
      break
    }
    lifeT -= attA
    isContinue = lifeT > 0
    if (!isContinue) {
      break
    }
  }
  println(result)
}
