import java.io.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;

public class Height extends DefaultHandler {
  int h = -1;
  int max = 0;

  public void startElement(String uri, String localName,
                           String qName, Attributes atts) {
    h++; 
    if (h>max) 
      max = h;
  }

  public void endElement(String uri, String localName, String qName) {
    h--;
  }

  public void characters(char[] ch, int start, int length){
    if (h+1>max) 
      max = h+1;
  }

  public static void main(String[] args) {
    try {
      Height handler = new Height();
      XMLReader reader = XMLReaderFactory.createXMLReader();
      reader.setContentHandler(handler);
      reader.parse(args[0]); 
      System.out.println(handler.max);
    } catch (Exception e) { 
      System.err.println(e); 
    }
  }
}