Need Help On Ada95 Problem

[Will <willmann817@gmail.com>]

I am new to Ada and need help on an exercise for school.  Can anyone
help.  The problem is as follows ( you can skip all the build up
background A Christmas Story references):

Problem 1: Secret Decoder Ring

You may remember Ralphie's disappointment when he received his Little
Orphan Annie Secret Decoder Ring.
What you may not realize is that, after Ralphie threw away his ring,
his brother Randy dug it out of the trash. Randy grew up to run the IT
department of his small hometown bank, and was responsible for storing
the 4-digit Personal Identification Numbers (PINs) chosen by his
bank's customers. He knew better than to store these PINs in the
clear, so he encrypted them using Ralphie's ring.

The decoder ring had two wheels, one printed with letters and one
printed with numbers. In the video clip, you see Ralphie decoding the
numbers read on the radio, looking up each number and copying down the
corresponding letter. Randy uses the ring in a similar way, but
instead of disguising letters as numbers, he does the reverse,
disguising numbers as letters. To encrypt a PIN, he finds each digit
on the wheel, and turns it into a letter. (The ring contains some two-
digit numbers as well, but he ignores those, using only the single-
digit numbers.)

Here is a small portion of the decoder ring:

     number wheel ->    0  1  2  3  4  5  6  7  8  9
     letter wheel ->    U  R  O  V  A  L  T  I  N  E

So, for example, Randy encrypts the PIN 9537 as ELVI.

Complete the function Encrypt(PIN) that takes a 4-digit PIN (as a
string) and returns the corresponding 4-letter code (also as a
string).

Note: It would be possible to convert digits to letters using a giant
IF statement, but don't do this. Instead, the letter wheel is given to
you as a string, so use each digit to read the appropriate letter from
the string.