import java.util.*;
public class Main{
	public static void main(String[] args){
      Scanner i = new Scanner(System.in);
      int A = i.nextInt();
      int B = i.nextInt();
      int C = i.nextInt();
      int D = i.nextInt();
      boolean ta = false;
      for(int j=1;true;j++){
      	C-=B;
        if(C<=0){ta=true;break;}
        A-=D;
        if(A<=0){ta=false;break;}
      }
      System.out.println(ta?"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