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)
  var n: Int = 0
  var continue: Boolean = true
  
  while (continue) {
    if (a - d * n > 0 && c - b * (n + 1) <= 0) {
      print("Yes")
      continue = false
    } else if (a - d * n <= 0 && c - b * (n + 1) > 0) {
      print("No")
      continue = false
    } else {
      n = n + 1
    }
  }
}
