import java.util.*;
public class Main{
	public static void main(String[] args){
    	Scanner sc = new Scanner(System.in);
      	int a = sc.nextInt();
      	int b = sc.nextInt();
      	int c = sc.nextInt();
      	int d = sc.nextInt();
      
      	while(true){
        	c -= b;
          	if(c <= 0){
            	System.out.println("Yes");
              	break;
            }
            a -= d;
            if(a <= 0){
            	System.out.println("No");
              	break;
            }                     
        }
    }
}
/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