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.
One example: ['8129', 'a', '4245', 'y', 'm', 'a']
Solution is here: a, m, y
Explanation: Here, the unique alphabets in the list are 'a', 'y', and 'm', hence their sorted order is 'a, m, y'.

Now, solve this: ['9669', '7973', '3945', '2651', '3159', 's', 's', 'g', 'p', '4351', 'g', '3207', 'f']
Solution:

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
f, g, p, s