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:
['1429', '7273']
answer:
-1


question:
['r', 'y', 'c', '3211', '9245', '8459', '8521', '5781', 'w', 's', 'd', '5299', 'a', 'y', 'g', 'm', '6435', '8605', 'e', 'h', '6871', 's', '387', 'l', '5829', 'e', 'd', '9545', '2945', 'k', 'v', 't', '8449', '2199', 'm', '2599', '1489', '6623', 'x', 'l']
answer:
a, c, d, e, g, h, k, l, m, r, s, t, v, w, x, y


question:
['5843', 't', '5869', '2795', 'r', '1567', 'i', 'h', 'a', '5551', '5347', '1029', 'f', 'e', '9617', '7363', '3921', '1585', 't', '1317', '3457', 's', 'u', 'k', '5301', 'u', '7929', '8181', '7691', 'j', 'a', 's', '2303', 'b', '5863', '715', '7385', 'n', '7819', 'l', '4821', '7293', '4633', '877', '5873']
answer:

a, b, e, f, h, i, j, k, l, n, r, s, t, u