In the attached algorithm for computing the quotient and remainder between two numbers, the third-to-last line (`q := -(q + 1)`) confuses me. 

[algorithm](https://i.stack.imgur.com/JcQQv.png)

Assuming the second begin...end is an iterative structure, and if `q` starts at zero, it will alternate between 0 and -1. So that's not the right interpretation. Is it not an iterative structure?