比赛录屏
\(A. Cover in Water\)
https://codeforces.com/contest/1900/submission/234430348
\(B. Laura and Operations\)
https://codeforces.com/contest/1900/submission/234447465
https://codeforces.com/contest/1900/submission/234430348
https://codeforces.com/contest/1900/submission/234447465