import java.util.Scanner
import kotlin.math.*

fun main() {
	val scn = Scanner(System.`in`)
	val a = scn.nextInt()
	val b = scn.nextDouble()
	val c = scn.nextInt()
	val d = scn.nextDouble()
	println(if (ceil(a/d) >= ceil(c/b)) "Yes" else "No")
}