import java.util.Scanner;
public class Main {
    public static void main(String[] args) throws Exception {
       Scanner stdIn= new Scanner(System.in);

        int a = stdIn.nextInt();
        int b = stdIn.nextInt();
        int c = stdIn.nextInt();
        int d = stdIn.nextInt();
        for(;;){
            if(c<=b){
                System.out.println("Yes");
                break;
            }
            c=c-b;
            if(a<=d){
                 System.out.println("No");
                break;
            }
            a=a-d;
        }
    }
}

/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