Hello Codeforces community!

I have a suggestion that I believe could improve the debugging experience on Codeforces, especially for those practicing problems.

Currently, when a submission fails, Codeforces only tells us which test case failed but does not specify which part of the test case caused the wrong answer. This makes debugging quite difficult, especially when a test case contains multiple queries or operations.

Suggestion It would be helpful if Codeforces could display the exact sub-part of the test case that causes the wrong answer instead of just showing the entire input. For example:

If a test case consists of multiple queries, indicate which specific query caused the failure. If the error happens at a specific index in an array, highlight that index. Maybe an optional "debug mode" could be enabled for practice problems to provide such insights. Possible Concerns I understand that revealing too much information might go against the competitive programming spirit, and implementing this in live contests might be impractical due to performance concerns. However, adding this feature for practice problems could significantly improve learning and debugging efficiency.

What do you all think? Would this be a useful feature? Looking forward to your thoughts!