unable to run sudo apt-get update

Since a very long time i am unable to use the sudo apt-get update command. I am using ubuntu 18.10(Also I use kubuntu). And running the above command prints the following on the terminal screen.

Hit:1 http://mirror.cse.iitk.ac.in/ubuntu cosmic InRelease Get:2 http://mirror.cse.iitk.ac.in/ubuntu cosmic-updates InRelease [88.7 kB] Get:3 http://mirror.cse.iitk.ac.in/ubuntu cosmic-backports InRelease [74.6 kB]                                             Ign:4 http://dl.google.com/linux/chrome/deb stable InRelease                                                              Ign:5 http://in.archive.ubuntu.com/ubuntu artful-updates InRelease                   Hit:6 http://dl.google.com/linux/chrome/deb stable Release     Err:8 http://in.archive.ubuntu.com/ubuntu artful-updates Release   404  Not Found [IP: 80] Get:9 http://security.ubuntu.com/ubuntu cosmic-security InRelease [88.7 kB] Reading package lists... Done       E: The repository 'http://in.archive.ubuntu.com/ubuntu artful-updates Release' no longer has a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.