Today I managed to solve 2020E - Матожидание квадрата and got passed barely within the time limit using C++17. Here is the submission 284264092, and as you see that it runs for 3900+ ms, while the TL is 4000 ms.

However when I selected C++20 and submitted, I found that the execution time was < 1000 ms. 284263872

So can anyone tell me what causes the difference?