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:
['1367', 'h', '4153', '1587', 'h', 'b', 'n', 'u', 'n']
answer:
b, h, n, u


question:
['4927', 'h', 'x', '4719', 'j', 'f', '7797', 'l', 'i', 'q', 'x', 'i', 'k', '3215', 'k', '1625', 'g', 't', 'i', 'w', 'n', '6659', '8355', '831', 'h', '9723']
answer:
f, g, h, i, j, k, l, n, q, t, w, x


question:
['q', 'm', 'k', 'r', 'f', 'r', 'l', '1941', '5793', 'n', 'c', 'x', 't', '7153', 'v', '6875', '6859', '5783', 'u', '7535', '1291', '8885', 'p', 'v', 'h', 'o', '9581', 'o', 'l', '3307', '9317']
answer:

c, f, h, k, l, m, n, o, p, q, r, t, u, v, x