g ++ is not installed what is wrong, what to do?

Question

Computer networks

This is what it says during installation

Answer 1

If you really did not touch anything, then the ENERGY server program obviously does not work.
Perhaps the computer rebooted (there was a power outage), and the program was once launched manually.
Or for some other reason, it was unloaded from memory.
It is unlikely that something more accurate can be assumed from the described symptoms.

Answer 2

13.04 is deprecated and not supported. Not immediately, but the repositories are also deleted (more precisely, they are transferred to other addresses).
Update.

Answer 3

The repository is dead, you need to select other servers in /etc/apt/sources.list and everything will work.

Answer 4

Russian language!