import java.util.*;
import java.util.HashSet;
import java.util.Map;
import java.util.HashMap;
import java.util.ArrayList;
import java.util.List;
import java.util.Arrays;
import java.util.Scanner;


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 (a > 0 || c > 0){
            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