Today while solving Sereja and Brackets I faced something strange and unexpected.
First I submitted my code in C++20. Submission: https://codeforces.com/contest/380/submission/165753528 (WA) This gave me WA verdict. Then I submitted the exact same code with C++14. Submission: https://codeforces.com/contest/380/submission/165754010 (AC)

I am puzzled why exact identical code give me different verdicts. I also compiled my code with many flags to catch common possible errors, but I got none locally and on custom invocation. Can somebody tell what exactly is causing this difference in verdict?