import java.util.Scanner

object Yukicoder extends App {
  val sc = new Scanner(System.in)
  val H = sc.nextLong()
  val W = sc.nextLong()
  val N = sc.nextLong()
  val K = sc.nextLong()

  val field = H * W
  val result = if (field >= K && (field - K) % N == 0) "YES" else "NO"
  println(result)
}