In this chapter I did not use any external libraries. Still, once you read the problem description you may decide to do otherwise. In that case don’t let me stop you.
I recommend you try to solve the task on your own first. Once you finish you may compare your solution with the one in this chapter (with explanations) or with the code snippets (without explanations).
A reminder of how to deal with packages and *.toml files can be found here.