The algs4 directory will be the "top-level" directory for your IntelliJ IDEA project.
Note that depending on how you extract the ZIP archive, you may have two algs4 directories, one inside the other. The one we want is the inner directory.
It should contain a subdirectory named src and a file named pom.xml.
Do not edit the pom.xml file.
At this point, do not change the contents of the project directories or any files under the project directory.
If you reopen any directory in IntelliJ IDEA, it must be this (possibly inner) top-level directory!
