Rejudging of the contest after the contest is a VERY BAD THING! I am SURE that a lot of people who found solution for problem F can find error and write own sqrt function for int64. BUT if you have not tests that fails this on the contest you CAN NOT do rejudge after IT. YOU CAN CHANGE THE DESCRIPTION OF THE PROBLEM TO SATISFY THE DATA SET BUT YOU CAN NOT CHANGE DATA SET! In this case results of the contest is not objective at all.
We apologize to all participants of the online contest whose submit during the contest lost AC verdict. Adding new tests to the problems of Timus Online Judge is a usual rule of this site, but we agree that the rejudge of the contest is not fair thing. I'll try to explain why we he had to rejudge this problem.
Because of technical error only 3 first tests from this problem's test set were installed to the Timus Online Judge. Unfortunately we have found this error only after the contest was finished. Now this problem has all tests that were prepared for the contest by its author. No new tests were added as a result of investigation of AC solutions of the contest.