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:
['2329', 'i']
answer:
i


question:
['1593', '8165', 'q', '6689', 'b', 'r', '373', 'g', '6505', '415', '495', 'j', 'j', 'f']
answer:
b, f, g, j, q, r


question:
['f', 'n', '5515', '7357', '899', 'a', '7121', '7539', 'k', '9937', '6359', '3747', 'p', 'y', 'u', '2969', 'p', '5543', '3687', '9233', 'z', 'i', '2937', '3811', '3399', 'm', '2039', '559', '2989', '4803', 's', '7959', '4165', 'n', '2205', '5405', 'u', 'w', '5617', 'k', '5683']
answer:

a, f, i, k, m, n, p, s, u, w, y, z