Code:
#!C:/Python27/python.exe

import cgi
form = cgi.FieldStorage()

a=int(form.getvalue('a','0'),0)
b=int(form.getvalue('b','0'),0)


print """Content-type: text/html

<html>
  <head>
    <title>Greeting Page</title>
  </head>
  <b><h1>Welcome!</h1></b>
  <body>
...