I just can't figure out why this has runtime error. https://codeforces.net/contest/1932/submission/259281147

I am 17 and I am preparing for the British Informatics Olympiad. When I try the BIO R2 questions, they don't seem all that difficult. Could someone please take a look at the BIO R2 questions (https://www.olympiad.org.uk/papers/2023/final/round_two.html) and tell me the difficulty level (in codeforces rating or smth). Apologies for the inconvenience.