While trying to solve 2108D - Needle in a Numstack, I encountered a bug I could not understand. Here is the submission 329129022. Codeforces says it's an out of bound error on line 32, but I suspect that this is coming from errors that were accumulated earlier. Can someone help me identify the error? Thanks in advance.

In today's E problem, my submission used exactly n-1 queries for each n to give out the answer. Can this be proven to be the least number of queries needed or is a better bound achievable?