Train station
=============

The head of the `Sant Ts` train station has designed a system to
distribute the different commuter trains between the different station
tracks. There are 4 train lines: 1, 2, 3 and 4 and two possible
orientations, N (North) and S (South). The distribution rules are the
following:

-  Line 1 North --> track 1
-  Line 1 South --> track 5
-  Line 2 North --> track 4
-  Line 2 South --> track 9
-  Line 3 North --> track 12
-  Line 3 South --> track 2
-  Line 4 North --> track 10
-  Line 4 South --> track 7

Write the function :py:func:`stop` that gets an integer that
represents the train line and a letter (string) that represents the
orientation and returns the corresponding track number (integer). If
either the line or the orientation are not valid, the function must
return 0. Save this function into a file named :file:`stop.py`. Examples:

   .. literalinclude:: test-stop.txt
      :language: python3
      :lines: 2-

   .. note::

      More tests are provided in the :download:`test-stop.txt <test-stop.txt>`

.. rubric:: Solutions

A solution of these functions is provided in the :download:`stop.py
<solutions/stop.py>`