import java.util.Scanner;

public class Main{
  public static void main(String[] args){
    
    Scanner scanner = new Scanner(System.in);
    int A = scanner.nextInt();
    int B = scanner.nextInt();
    int C = scanner.nextInt();
    int D = scanner.nextInt();
    
    double X = Math.ceil((double)C/(double)B);
    double Y = Math.ceil((double)A/(double)D);
    
    if(X <= Y){
      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