import java.io.*;
import java.lang.*;
import java.util.*;
public class Main{  
    public static void main(String[] args) throws IOException{
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        String[] str=br.readLine().split(" ");
        long A=Long.parseLong(str[0]);
        long B=Long.parseLong(str[1]);
        long C=Long.parseLong(str[2]);
        long D=Long.parseLong(str[3]);
        long E=(A%D==0)?A/D:A/D+1;
        long F=(C%B==0)?C/B:C/B+1;
        if(F<=E) 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