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:
['z', 'm', 'n', 'u', '9159', '7931', '5401', '1383', '8195', 't', 'x', 'q', 'r', '2535', 's', 'j', 'c', '8123', '2429', '5581', 'k', 'c', 't', 'i', 'm', 'o', 't', 'q', '4819', 't', '1649', 'r', 'y', 'z', '8813', '7451', '199', 'o', 'x', 's', 's', '6747']
answer:
c, i, j, k, m, n, o, q, r, s, t, u, x, y, z


question:
['7013', '8755', 'u', '9377', 'n', '6997', '507', '8557', '9745', 'g', '3019', '93', 'l', '1219', 'a', '393', '2573', 'q', 'b', '6101', 'e']
answer:
a, b, e, g, l, n, q, u


question:
['6783', '1499', '8413', '7467', 'z', 'n', 'm', '8049', '8425', '3741', 'w', '2683', 'e', 'z', 'w', '7223', 'f', 'g', '3759', '5849', '519', 'r', '1013', '3733', 'v']
answer:

e, f, g, m, n, r, v, w, z