import java.util.ArrayList;
import java.util.Scanner;

public class Main {
	

	
	public static void main(String[] args) {

		
		Scanner s = new Scanner(System.in);
		
			int a = s.nextInt();
			int b = s.nextInt();
			int c = s.nextInt();
			int d = s.nextInt();
			
			int ans1=0,ans2=0;
			if(a%d==0) {
				ans1=a/d;
			}
			else {
				ans1=a/d+1;
			}
			if(c%b==0) {
				ans2 = c/b;
			}
			else {
				ans2 = c/b+1;
			}
			if(ans1>=ans2) {
				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