import java.io.IOException;
import java.io.PrintStream;
import java.util.Scanner;

public class Main {
	static PrintStream o = System.out;
	
	public static void main(String[] args) throws IOException {
		Scanner sc = new Scanner(System.in);
		short thealth = sc.nextShort();
		short tattack = sc.nextShort();
		short ahealth = sc.nextShort();
		short aattack = sc.nextShort();
		while (true) {
			ahealth -= tattack;
			if (ahealth <= 0) {
				o.println("Yes");
				break;
			}
			thealth -= aattack;
			if (thealth <= 0) {
				o.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