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A pen at the briefing, a dressing gown from the hotel ... what a world it is
We are not being caught up
bzdyn
Imagine you need to mail an item (e.g. a book) to a friend. However, you live in a country where any item sent by mail is bound to be stolen,
unless it is in a box locked with a padlock. You have locks, but you also have the keys to them. Your friend also has locks (other locks) and the keys to them.
In order to open or close the lock you must have a key (locks do not latch). The hinges on the box are narrow and only one lock fits in.
How do I pass a book to a friend by post in the minimum amount of operations?