This problem has been solved.

I can't submit my code for this. I guess the error is because that in the contest solutions can only be submited using kotlin 1.4, but there are only kotlin 1.6 and kotlin 1.7 in the language list now. Is it possible to change something a little? Apparently there are two ways to do this: 1. Add the language kotlin 1.4 to the language list again. 2. Change the rule of the contest a little, such as adding kotlin 1.6 or kotlin 1.7 to the language list for the contest.