How do I shorten the current directory path shown on terminal?

If I am in a deep directory, let’s say:

~/Desktop/Dropbox/School/2017/C/A3/

then when I open up terminal, it says

bob@bob-ubuntu:~/Desktop/Dropbox/School/2017/C/A3/$

and then I write my command.
That is very long, and every line I write in the terminal goes to the next line. I want to know if there’s a way so that it only displays my current directory. I want it to display:

bob@bob-ubuntu: A3/$

This way it’s much clear, and always I can do pwd to see my entire directory. I just don’t want the entire directory visible in terminal because it takes too much space.