Legs and Seats

The Seats ‘R’ Us factory produces chairs with four legs and stools with three legs. The style of seats and legs are all the same. This year, if all the leftover legs were put with leftover seats to make chairs, one seat would be left over without any legs. However, if all the leftover legs were put on the leftover seats to make stools, one leg would be left. How many more legs than seats are in the leftover inventory?

(Source: Mathematics Teaching in the Middle School, Sep 1997)