Write a program using while loop that 

asks the user for two integers (one by one or at the same time if you know how to handle it). Then it adds them and displays the sum.

Then the user is asked to enter yes if she wishes to perform the operation again, and otherwise if she enters anything other than yes the program terminates. The operation (described in the bullet above) is repeated, as long as the user enters yes.

How to achieve this by FOR loop?