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A famous set of computer problems involve verbal arithmetic.  In these problems,
you are given equations of words like:

send
+ more
------
money

or:

forty
ten
+   ten
-------
sixty

The goal is to find a single digit for each letter that makes the equation true.
Normal rules of number construction apply, so the first digit of a multi-digit
number should be nonzero and each letter represents a different digit.

This week's quiz is to build a program that reads in equations and outputs
solutions.  You can decide how complex of an equation you want to support, with
the examples above being the minimum implementation.

Here's a solution you can test against:

\$ ruby verbal_arithmetic.rb 'send+more=money'
s: 9
e: 5
n: 6
d: 7
m: 1
o: 0
r: 8
y: 2

```