import javax.xml.parsers.*;
import java.io.*;
import org.w3c.dom.*;
class Average {
public static void main(String args[]) {
if (args.length != 2) {
System.err.println("Usage: Average element file");
System.exit(1);
}
Document doc = null;
try {
// Create the DocumentBuilderFactory
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
// Create the document builder
DocumentBuilder db = dbf.newDocumentBuilder();
// Create DOM document from the file
doc = db.parse(new File(args[1]));
} catch (Exception e) {
System.err.println("Parsing failed: " + e);
System.exit(1);
}
NodeList nodes = doc.getElementsByTagName(args[0]);
double sum = 0.0;
for (int i = 0; i < nodes.getLength(); i++) {
String grade = nodes.item(i).getFirstChild().getNodeValue();
sum += (Integer.valueOf(grade)).doubleValue();
}
System.out.println(sum / nodes.getLength());
}
}