Q:
         
         
            
               Logical puzzle
            
                           
                  
You want to send a secret message to your friend Alex in the mail. But Sam, who you don't trust, has access to all your mail. So you put your message in a box with a lock. But you are not allowed to send a key! How can you get your message through securely?
               
                      
         
             Answer
                        - Send the box with the lock to Alex. 
- Alex can't open it, but can put another lock on the box. 
- Alex sends this box with the 2 locks back to you, you unlock your lock and send it back to Alex again.
- So there is just Alex's lock on the box and Alex can now open it.
          
         
         
         
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