Output of reference variable

If we are taking the value of a=10 than output will be
10
10
100
100

Now you may ask how?
Because we are taking r as a reference variable of a, whatever we change in r the change automatically transmit to a. To understand it more clearly please try to change the value of both a and r in the program. I bet after changing two or three variables in this program you have not any question if still there is any question you may email meat famoustar2001@yahoo.com