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:
['9923', 'x', '1901', 'v', '1459', '7503', '3829', '4929', 'k', 'c', '3329', '8793', 'n', 'a', '7249', 'b', 'l', 'l', 'm', 'p', 'b', 'a']
answer:
a, b, c, k, l, m, n, p, v, x


question:
['5463', '5683', 'w', '4071', '3997', 'i', '9677', 'q', 'l', 'v', 'w', '5325', '197', 'g', 'g', '3227', '3477']
answer:
g, i, l, q, v, w


question:
['4861', 'e', 'z', '1699', 'm', '5447', '7357', 'p', '8975', 'f', 'u', '9853', 't', '331', 'p', '69', 'n', '6711', 'y', 'l', 'y', 'l', '2965', 'm', 'j', 'u', '233', '1871', 'u', 'w', '9221', 't', 's', 'v', '9663', 'u', '309', 'p', 'l', '1215', '7337', '7581', 'b']
answer:

b, e, f, j, l, m, n, p, s, t, u, v, w, y, z