In this task, you are given an input list A comprising of numbers and alphabets. You need to extract and sort the unique alphabets in the list. The alphabets in the input list will only be in lowercase. Return -1 if there is no alphabet in the input list.

Let me give you an example: ['8129', 'a', '4245', 'y', 'm', 'a']
The answer to this example can be: a, m, y
Here is why: Here, the unique alphabets in the list are 'a', 'y', and 'm', hence their sorted order is 'a, m, y'.

OK. solve this:
['7727', '347', 'i', 'u', 'b', '7025', '5889', 'm', 'o', 'w', 'c', 'y', 'm', '9187', 'o', 'e', 'p', 'g', 'a', 'c']
Answer:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
a, b, c, e, g, i, m, o, p, u, w, y