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:
['333', 'b', '261', 'k', 'p', '7861']
answer:
b, k, p


question:
['c', 'r', 'i', 'f', '113', '2325', 'v', '5693', 'j', '4267', '1575', '7855', '5021', '1009', '8423', 'e', 'm', 'b', 'p', 'x', 'r', '9831', '2519', '9437', '7485', '2999', 'w', 'w', 'q', 't', 'x', '8583', '7027', '6209', '1823']
answer:

b, c, e, f, i, j, m, p, q, r, t, v, w, x