import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;

public class Three extends HttpServlet {

  public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    response.setContentType("text/html");

    PrintWriter out = response.getWriter();

    String message, good, total, n1, n2, me;

    me = request.getContextPath() + request.getServletPath();

    message = request.getParameter("message");
    good = request.getParameter("good");
    total = request.getParameter("total");
    n1 = request.getParameter("n1");
    n2 = request.getParameter("n2");

    if (message == null) {

      n1 = (int)(Math.random() * 100 - 50) + "";
      n2 = (int)(Math.random() * 100 - 50) + "";
      good = "0";
      total = "0";
      message = "Welcome, score is: " + good + "/" + total + ". What is " + n1 + " + " + n2 + "?";

    } else {

      String answer = request.getParameter("answer");

      if (Integer.parseInt(answer) == Integer.parseInt(n1) + Integer.parseInt(n2)) {
        good = (Integer.parseInt(good) + 1) + "";
        message = "Good answer. ";
      } else {
        message = "Not good. ";
      }
      total = Integer.parseInt(total) + 1 + "";
      message +=  "score is: " + good + "/" + total + ". ";
      n1 = (int)(Math.random() * 100 - 50) + "";
      n2 = (int)(Math.random() * 100 - 50) + "";
      message += " What is " + n1 + " + " + n2 + "?";

    }

    out.println(

"<form action=\"" + me + "\">" +
"  " + message + "<p>" +
"  Type your answer here: <input type=\"text\" name=\"answer\"> <p> " +
"  Push <input type=\"submit\" value=\"Proceed\"> when ready. " +
"  <input type=\"hidden\" name=\"message\" value=\"" + message + "\">" +
"  <input type=\"hidden\" name=\"good\" value=\"" + good + "\">" +
"  <input type=\"hidden\" name=\"total\" value=\"" + total + "\">" +
"  <input type=\"hidden\" name=\"n1\" value=\"" + n1 + "\">" +
"  <input type=\"hidden\" name=\"n2\" value=\"" + n2 + "\">" +
"</form>"

    );

  }
}