Lab Activity # 5Lab Activity # 5
Implement and test a Fortran 90 program which has the following features:
  When the user runs the program he/she gets the following displayed on the 
  screen: 
Enter a positive integer (k).
After the user enters a value for k (the integer number will be assigned to a 
variable called k.), he/she gets the following menu
 
Press 1 for  the sum of the integers from 1 to k.
Press 2 for k!
 
  If the user selects 1 or 2 he/she gets the job described above performed and 
  the result will be displayed on the screen. Then, the program displays the 
  following: 
Continue? If not, press “n” or “N”, else press any other key.
If the user hits n or N, then the program stops running. If the user hits any 
other key, the program repeats the whole process (i.e. goes back to step #1.)
  If the user hits a key different than 1 or 2, then he/she must get the 
  following message: 
Invalid Option
            And then, the program repeats the whole process (i.e. goes back to 
step #1).