Due to improper shutdown file system check has failed while loading ubuntu

In order to solve the error you need to correct the file system manually. So the ubuntu will ask you correct the file system manually. To do the same follow the below steps

1. If you dont know the root credentials

Press ctrl + alt + delete then it will ask the user name, password.

Enter the credentials that you have then execute the following command to correct the file system

sudo fsck then it will ask so many prompts give the inputs of your choice [yes/no]

After that execute this command sudo reboot, Now the ubuntu will load properly

Note: I dont know is it correct or not but it works for me.