instruction:
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.
question:
['q', 'g', 's', 'g', 'z', '987', '777']
answer:
g, q, s, z


question:
['d', '771', '4193', 'e', '1537', 'a', 'q']
answer:
a, d, e, q


question:
['b', '2133', '5183', 'r', '5825', 'm', '4799', '6567', '8823', '4039', '5131', '2015', '9259', '3441', 'w', 's', 'i', 'p', '5743', 'w', 'm', 'y']
answer:

b, i, m, p, r, s, w, y