import java.util.*;

public class Main {
	public static void main(String[] args){
	Scanner scn = new Scanner(System.in);
	int a = scn.nextInt();
      int b = scn.nextInt();
      int c = scn.nextInt();
      int d = scn.nextInt();
      int x = c/b;
      int y = a/d;
      int xx = c%b;
      int yy = a%d;
      if(xx != 0){
        x = x+1;
      }
      if(yy != 0){
        y = y+1;
      }
      if(x<=y){
        System.out.println("Yes");
      }else{
        System.out.println("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