import java.util.Scanner;
class Main{
    public static void main(String args[]){
        Scanner scan = new Scanner(System.in);
        int Thp = scan.nextInt();
        int Tattack = scan.nextInt();
        int Ahp = scan.nextInt();
        int Aattack = scan.nextInt();
        while(true){
            if((Ahp - Tattack) > 0){
                Ahp = Ahp - Tattack;
             }else{
                 System.out.println("Yes");
                 break;     
             }
             if((Thp - Aattack) > 0){
                 Thp = Thp - Aattack;
             }else{
                 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