Codeforces Round 909 (Div. 3) The A problem involved game theory, and it was quickly recognized due to the remainder being 3. However, there was a delay of 4 minutes in posting the problem due to internet issues. The B problem required a combination of block splitting and prefix sum techniques. Due to a lack of clarity in my thought process during the block splitting loop and issues related to array size and the long long (ll) data type, I struggled to pass the test cases. Eventually, I resolved the B problem after 1 hour and 31 minutes, but the penalty time was high. I briefly glanced at the C problem during the contest and identified it as a dynamic programming (DP) problem. However, I was uncertain about my ability to solve it at that moment, so I decided to skip it and try the D problem. The D problem involved finding patterns where the exponent sum and the base taken in reverse were the same. Despite attempting manual calculations on paper and using examples, I couldn't find a clear pattern. In the end, my ranking for A and B was 8805, with an increase of 426 points, primarily due to the extended time spent on B. My gf also participated in the round, ranking 9738 with a rating increase of 414. After the contest, my girlfriend and I solved the C problem together early in the morning. It turned out to be a straightforward DP problem, and if I had focused on solving C during the contest without looking at D, I might have been able to solve it in the competition.