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:
['4637', 'f', '2639', '8623', 'w', 'e', 'k', '5503', 'x', '6633', '7553', '1455', 'u', '1773', 'r', 'u', '1489', 'u', '1303', '9683', 'z', '565', '7041', 'x', 'z', '9431', 'k', 'v', 'j', 'z', '5469', '5665', '4089', '4951', '8263', '5675', '4095', '7745', 'z', '2437', 'd', 'e', 'w']
answer:
d, e, f, j, k, r, u, v, w, x, z


question:
['c', '7039', 'g', '1899', 'r', '507', 'c', '2587', '3865', '1729', '3927', 'r', '3535', '2791', 'm', 'l', 'r']
answer:
c, g, l, m, r


question:
['3007', '8663', 'o', 'j', 'c', 'f', 'z', '3859', '1761', 'h', '2685', '129', 'm', 'c', 'm', '1543', 'l', 'c', '4491', 'r', 'd', 'w', '6025', '8849', '6557', '3197', 'y', '7111']
answer:

c, d, f, h, j, l, m, o, r, w, y, z