MYSTERY PROGRAM MINI-CHALLENGE
------------------------------

--> S/SX/G/GX

The following bizarre-looking User RPL program takes any real integer
and returns the number of bits required to express it in binary.
Example: input 6, it outputs 3, because 6 requires 3 bits (viz. 110).

Mini-Challenge: figure out why it works.

Have fun!  -jkh-

%%HP: T(3);
\<< 0 1 ROT FOR
  DEPTH 1 +
  DEPTH STEP
\>>