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:
['7055', '2573', '1713', 'x', 'm']
answer:
m, x


question:
['4031', 't', 'o', 'c', 'x', '3007', '8329', '6345', '1267', '1017', 'o', 'x', 'l', '4129', 'd', '1987', '487', 'o', 'g', 'j', 'v', 'x', '3983', 'f', 'g', '5759', 'k', 'i', 'o', 'b', 'n', '683', 'j', 'o', 't', '4361', 'u']
answer:
b, c, d, f, g, i, j, k, l, n, o, t, u, v, x


question:
['r', 'v', 'd', '3095', 'l', 'k', 'x', '5535', 'h', '1505', 'g', '8607', 'q', 'a', 'a', '3265', 'o', '6639', 'f', '9161', 'i', '4775', 'k', '9851', '8025', '2333', '9747', 'x', '2507', 'w', 'a', '4865', 'e', 'w', 'r', '2747', '3187', '2241', '9339']
answer:

a, d, e, f, g, h, i, k, l, o, q, r, v, w, x