import java.io.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;
import org.xml.sax.*;

// The main method must be in a class named "Main".
class Main {
    public static void main(String[] args) {
        
        String xmlStr = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>" +
                        "<books>" +
                        "   <book>" +
                        "       <author>" +
                        "           <firstName>Bert</firstName>" +
                        "           <id>1</id>" +
                        "           <lastName>Bates</lastName>" +
                        "       </author>" +
                        "       <isbn>ISBN-45565-45</isbn>" +
                        "       <title>Head First Java</title>" +
                        "   </book>" +
                        "</books>";


        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();  
        DocumentBuilder builder;  
        try  
        {  
            builder = factory.newDocumentBuilder();  
            Document doc = builder.parse( new InputSource( new StringReader( xmlStr ) ) ); 

            var node = doc
                .getElementsByTagName("isbn")
                .item(0)
                .getTextContent();
                
            System.out.println(node); 
                
        } catch (Exception e) {  
            System.out.println(e);  
        } 

    }
}