import java.util.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt(),
            b = sc.nextInt(),
            c = sc.nextInt(),
            d = sc.nextInt();

        int s = 0;
        while (a > 0 && c > 0) {
            if (s == 0) {
                c -= b;
                s = 1;
            }
            else {
                a -= d;
                s = 0;
            }
        }

        System.out.println(a > 0 ? "Yes" : "No");
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz