SUP Squad!

The super special secret SUP Squad is here!

Step one: pick any whole number! That'll get you started.

Step two: write that number backwards! And now we're on our way.

Step three: subtract the two numbers! Don't suck at math.

Step four: add up the digits! We're gonna go cray-cray!

Step five: We go into overdrive as you do it again and again, and its absolute value should be zero or nine.