Can you solve the risky disk riddle?

Your antivirus squad is up against a code that's hijacked your mainframe. What you've learned from other infected systems, right before they went dark, is that it likes to toy with antivirus agents in a very peculiar way— and you're the agent that's been selected to go up against the malware. Can you figure out which disk that runs your mainframe has been corrupted? James Tanton shows how. [Directed by Igor Coric, Artrake Studio, narrated by Addison Anderson, music by Cem Misirlioglu].