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:
['491', '229', 'g', '6677', '4793', 'h', 'x', 'a', '2333', 'u', 'l', '785', 'p', '7331', '653', '5193', '5415', '8417', 'v']
answer:
a, g, h, l, p, u, v, x


question:
['7591', '7521', 'm', '1429', 'x']
answer:
m, x


question:
['b', 'w', '343', 'g', 'i', 'e', '8003', '5553', '2865', 'r', '1117', 'c', '6635', '5919', 'h', 'i', '6745', '9859', 'a', '6583', 'r', 'o', '6935', '6623', 'k', '7541', '3355', 't', '8047', 'n', 'u', 'f', '1793', 's', 'p', '9077', 'n', 'g', '8673', '6391', '2897', '2287', '4821', '8309']
answer:

a, b, c, e, f, g, h, i, k, n, o, p, r, s, t, u, w