[Harry says] Can you help?

The new site and server seem to be behaving, but we would like to test the submission system so we have set up a "not really Challenge 0" puzzle for you to try. See if you can work out the answer to the following question, then submit it using the part A form on the "submit your solutions" page. The Stolen Code: A locksmith has changed the lock on Harry's secret office to use a new electronic pin code. Unfortunately someone has stolen the piece of paper on which the code is written so Harry has to reset it. To do so he needs the old code, but he can't remember it. All he remembers is that it is the sum of the first 100 odd numbers. Once you have submitted it you should receive an email at your registered address confirming submission, and a little time later you should get a feedback email telling you if your submission is right or not. Let us know if you have any problems. Thanks for your help.