new to prime ARG? INV?

[DrD]

Like most things in n life, experience is key. The toolbox key has access to the catalog of commands. ARG() is listed there. That's probably your best hope, if you're stranded on a deserted island with just time and your prime.

The search option on this forum can be helpful also. The learning curve can be a little steep at times, and the prime isn't the rpn calc that you're probably used to. So getting familiar with it might need to be taken in small steps.