Actually, in the initial case, my ctrl and shift button were not working properly, so I followed the answers posted in this link: Shift keys not working properly, I run the following commands:
sudo dpkg-reconfigure keyboard-configuration
sudo apt-get install console-common
sudo dpkg-reconfigure console-data
But when I restarted, a different kind of login screen is getting displayed, and when I tried logging in with password, I am getting this message: "unable to get the valid context for (user)" and jumping back to same screen again.