I would like to know how to get the long Ubuntu based version in Elementary OS

Output of lsb_release -a -u:

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.04 LTS
Release:    14.04
Codename:   trusty

And lsb_release -a :

No LSB modules are available.
Distributor ID: elementary OS
Description:    elementary OS Freya
Release:    0.3.2
Codename:   freya

As you can see none of the commands have the long Ubuntu version (like 14.04.3)