Test if you have necessary packages:

$ which pdflatex
$ which convert

If you don't have it, install it. The program convert is part of the imagemagick package, thus to install both packages i.e. on Debian you will have to run command apt install imagemagick pdflatex as root.

Create virtualenv and install python packages:

$ virtualenv -p python3.5 counter-env3
$ . counter-env3/bin/activate
$ pip install -r requirements.txt

Run server:

$ cd web
$ python server.py &

Visit site: 0.0.0.0:5000 in your browser.

Enjoy :)