Dec26

@leapfrog-dipendra  @bhuwang  @adhpawal  @anishmanandhar @utsabneupane @Satish-Gupta @nerisa 
Try to catch specific exception if you know what sort of exception might occur.
For example in this scanner, program is expecting user to give sum numbers, what if user inputs string, 
You can catch specfic exception for e.g InputMismatchException , Please check it