I solved this problem. My first submission is in Clang++17 Diagnostics. I got M.L.E. My second submission is in GNU C++17. This time I got A.C.

What other online judge (OJ) do you use for contest? I wanna participate in contest in other online judge to see the variety of problem and coding environment. There are some good OJ where regular contests are held such as: Codechef, Atcoder, Hackerearth, Leetcode etc. Which one of these whould be the best choice as secondary oj for regular contest?