import java.util.*

fun main(args: Array<String>) {
    val scan = Scanner(System.`in`)
    var arr = scan.nextLine().split(" ").map{ it.trim().toInt() }.toTypedArray()
    var a =arr[0]
    var b =arr[1]
    var c =arr[2]
    var d =arr[3]
    var vari = 1
    while(a>0 && c>0)
    {
        if(vari==1)
        {
            c-=b
            vari=2
        }
        else
        {
            a-=d
            vari=1
        }
    }
   // println("$a $c ")
    if(c<1)
        println("Yes")
    else
        println("No")
}
