I see, so you are using a different model for computation that does not use rational numbers, but instead pairs of integers. From a computational point of view, that makes a lot of sense, disallowing catalysts is quite annoying, but I would not call this Fractran, instead I would call it something like a prioritized chemical reaction network or something like this. The wikipedia article explicitly states:

> The same variable cannot be both decremented and incremented in a single instruction (otherwise the fraction representing that instruction would not be in its lowest terms). Therefore each FRACTRAN instruction consumes variables as it tests them.