import java.util.Scanner;

public class Main{
  public static void main(String args[]){
    Scanner sc = new Scanner(System.in);
    int a = sc.nextInt();
    int b = sc.nextInt();
    int c = sc.nextInt();
    int d = sc.nextInt();    
    double ad = (double)a / d;
    double cd = (double)c / b;
    int ansa = 0;
    int ansc = 0;
    if(ad % 1 != 0){
      ad++;
      ansa = (int)ad;
    }else{
      ansa = (int)ad;
    }
    
    if(cd % 1 != 0){
      cd++;
       ansc = (int)cd;
    }else{
      ansc = (int)cd;
    }  
    if(ansa >= ansc){
      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