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There are $64$ hard drives each with one extra bit ("flag"), the value of which you don't know (it can be '$0$' or '$1$'). One hard drive is infected with virus that you need to heal.
You have two softwares in your disposal to help you: a detector and an antivirus. The detector always identifies the infected hard drive, but may only set/unset one flag (out of the $64$ flags) and can peek to see the values of each flag. The antivirus can inspect each flag as well, but may only attempt to heal one hard drive. If the antivirus is given a clean hard drive it stays clean, and if it is given an infected one it heals it.
How would you coordinate the work of the detector and the antivirus such that you always fulfill your objective?