import java.util.Scanner;

public class Main {
    
    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);

        int takahashiHP = scanner.nextInt();
        int takahashiAttack = scanner.nextInt();

        int aokiHP = scanner.nextInt();
        int aokiAttack = scanner.nextInt();
        
        while(true) {
            aokiHP -= takahashiAttack;
            if(aokiHP <= 0) {
                System.out.println("Yes");
                break;
            }
            takahashiHP -= aokiAttack;
            if(takahashiHP <= 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