The Riddle That Seems Impossible Even If You Know The Answer by Veritasium

This was a fun video to watch:

I honestly thought that they needed to have a code or something to hint other prisoners where the number was. Another solution i thought was that some prisoners were just able to open the even numbers or the odd numbers. I did not thought about the actual solution!

After watching the video tell me: were you as surprised as me with the solution?