There is a time clash between both contests to be held on 19th December 2017. Topcoder Single Round Match is at 21:30 IST and Codeforces Round #453 is at 21:05 IST. So, in this case, we have to choose any one of them. Therefore, I request to admin to please adjust the timings so that we can take part in both the contests.
Thank you & Happy Coding!!!