system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:how do you get cranes on to the tops of skyscrapers?
gpt
You send a small crane up, and use that to lift the big crane.  They break down into smaller pieces.

&#x200B;

Also there is a method by which a crane builds the structure *underneath itself*, lifting itself up with jacks as it builds the structure.