Write a solution to an olympiad or interview problem and get it marked like an examiner would: checkpoint by checkpoint, with the exact line where the argument breaks. Problems from the library are marked against their own mark scheme and examples, then checked a second time by an independent pass. Treat the result as a demanding second opinion, not an official mark.
1. The problem
Your own problems are marked against a general scheme, because there is no problem-specific mark scheme to compare with. Library problems are marked more reliably.
2. Your solution
3. Who marks it
Free marker
Marking takes two or three requests: a first marking, an independent check, and a re-mark if the check finds something serious. Each visitor has a daily allowance shared with the mock interviews. Your solution is sent to the model only to be marked; this site does not store it.
Claude, built in
Uses Claude's most capable reasoning model where your plan allows, with the two-pass check. Careful marking takes a minute or two.
Any chatbot
Pick your chatbot. The marking prompt is copied and the chatbot opens in a new tab.
Paste the prompt there and send it. Use its most capable reasoning mode if you can choose.
Copy the chatbot's whole reply, paste it below, and press Show report.
Second check (recommended)
A second, independent read catches steps the first marking credited too generously. Start a new chat for it, so the checker has not seen its own earlier reply.