Fizz Buzz sum
Given N, sum the integers 1 to N that are multiples of 3, or multiples of 5, but not both.
For example, if N=16, you would return
3+5+6+9+10+12 = 45. Note that you would not include 15 in the sum, as it is a multiple of both 3 and 5.
Put the sum in
r2, then execute the