Exercise: Arimu and Hats |2|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Our friend Arimu loves hats and wants to buy as many hats as possible.
Unfortunately, he can’t always afford all the hats in the store. So he
needs to spend his money wisely, to be able to purchase the maximum
number of hats.

Write a function named *buy_hats* which takes a *list of integers* as
the costs of hats and an *integer* as Arimu’s money. This function finds
the maximum number of hats Arimu can buy and returns it as an *integer*.

*Hint: You might want to rearrange the list of hats in the increasing
order of their prices.*

.. container:: sampleio

   Sample I/O:

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

.. code:: default

   >>> buy_hats([12, 3, 7, 5, 4, 8], 12)
   3

   >>> buy_hats([4, 3, 6, 2, 5, 5], 27)
   6