import java.util.*;
class Main
{
    public static void main(String args[])
    {
        Scanner ob=new Scanner(System.in);
        int ah=ob.nextInt();int as=ob.nextInt();
        int bh=ob.nextInt();int bs=ob.nextInt();
        int tak=(int)Math.ceil((double)bh/as);
        int akoi=(int)Math.ceil((double)ah/bs);
        System.out.println(tak<=akoi?"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