

fun main() {
    var (th, ta, ah, aa) = readLine()!!.split(" ").map { it.toInt() }
    var idx = 0

    while (th > 0 && ah > 0) {
        if(idx == 0) {
            ah -= ta
            if(ah <= 0) {
                print("Yes")
                return
            }
        } else {
            th -= aa
            if(th <= 0) {
                print("No")
                return
            }
        }
        idx = (idx + 1) % 2
    }




}