First, clone the project (THE DIRECTORY IS IMPORTANT FOR CALCULATING THE RETURN VALUE, SO PLEASE, FOLLOW THIS INSTRUCTIONS):
$ cd /home/user # the username is important, for now only "user" is tested
$ git clone git@github.com:Pablito2020/bufferoverflow-exploit.git practica
$ cd practica
Then, install the binaries and disable some stack protections:
$ sudo make install
Finally, run the exploit (if 70 isn't enough, try different numbers or create a loop that tries from 20 to 200):
$ ./exploit 70
If you want to see how you can overflow the version that uses puts instead of printf (which was disabled with the -fno-builtin-printf flag), you can check out the "gdb-only" branch.