Hi guys, i just found a new way to customize the "custom test" ide in codeforces. Just press "ctrl + ," and then you will see this screen, you can custom any thing on it, like a real ide. But refresh the page will restore any setting :((. Try it.

Hello guys, i have a question like this. Given an array has length n, n <= 10^7, a[i] <= 10^9. Number K <= 10^9. How i can count number of subarray has average sum equal to K. Thanks for your time.