Update 11-lists.md Working With the End exercise

Fix an error in the Working With the End exercise.

If a string has N elements, the most negative index that can be safely used is -N not -(N-1), corresponding to the [0] index.

>>> element = 'helium'
>>> print(element[-1])
m
>>> N = len(element)
>>> print(N)
6
>>> print(element[-(N-1)]) #This will give us the [1] index (e)
e
>>> print(element[-(N)])
h

Author: srappel

_episodes/11-lists.md

@@ -277,7 +277,7 @@ IndexError: string index out of range
 > > ~~~
 > > {: .output}
 > > 1.  A negative index begins at the final element. 
-> > 2.  `-(N - 1)` corresponds to the first index, which is the [0] index. 
+> > 2.  `-(N)` corresponds to the first index, which is the [0] index.
 > > 3.  It removes the final element of the list. 
 > > 4.  You could do the following: `print(values[0:-1])`
 > {: .solution}