import java.util.*;
import java.io.*;

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();

        boolean turn = true;
        while(true){
            if(turn){
                C -= B;
                turn = false;
            }else{
                A -= D;
                turn = true;
            }
            if(C <= 0) {
                System.out.println("Yes");
                break;
            }
            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