Exercise: Memento |2|
~~~~~~~~~~~~~~~~~~~~~

Assume that nowadays you suffer from not being able to remember things
that you used to. In order to strengthen your memory, you decide to
create a function that helps you to refresh your memory.

Write a function named *memento* that takes a string as a path of
possibly existing file. This function tries to read the file with the
given name. The function returns a *string* according to following
conditions:

-  If the file does not exist, the function must catch the exception and
   return ``"File not found, try again!"``.
-  If the file exists, read the file. if the content that is read
   contains only digits, the function must return the *string*
   ``"Finally you found the correct one! The password is: {number in the file}"``.
-  If there are non-numeric characters in the file, then the function
   must return ``"Wrong file, try again!"``.

**Note**: Any string methods that helps you to detect a non-numeric
character is forbidden. Instead, you can try to cast the content to an
*integer*.

.. container:: sampleio

   Sample I/O:

.. |2| image:: ../../figures/difficulty_five.png
   :class: difficulty

.. code:: default

   Content of the file "test1.txt":  
       dasdkjlkldsa9102801

   Content of the file "test2.txt":  
       15646456

   >>> memento("test.txt")
   'File not found, try again!'

   >>> memento("test1.txt")
   'Wrong file, try again!'

   >>> memento("test2.txt")
   'Finally you found the correct one! The password is: 15646456'