AtC以外のコンテストでは使っていそう

https://codeforces.com/profile/Leal_0
(コドフォは現在ダウンしている)
https://www.codechef.com/users/leal_al

https://discuss.codechef.com/t/flippre-editorial/123261
https://www.codechef.com/viewsolution/1150936960
https://www.codechef.com/viewsolution/1150938820
https://www.codechef.com/viewsolution/1150946910
AC
https://www.codechef.com/viewsolution/1150951411