How to find the number of odd numbers in a range?

so first you look at the top of range if it is odd then add all you do is add 1 if it is even then just leave it alone. Next, look at the bottom of the range, if it is odd then all you just do is subtract 1, again, if it is even then leave it alone. After that, you take the differences between the new even top and the new even bottom.
last you just divide it by two. that's how you find the number of odd numbers in a range.