Integer user$\_$num is read from input. Write a while loop that iterates while user$\_$num is non$-$negative. In each iteration:

Update value output$\_$num as follows:

If user$\_$num is even, subtract user$\_$num from output$\_$num.

Otherwise, add user$\_$num to output$\_$num.

Then, read the next integer from input into variable user$\_$num.