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:
['m', '7517', '9361', '9567', '8785', 'k', '5699', '3585', 'v', '1913', '1651', 'g', 'p', '2731', 'q', 'h', '467', 'r', '1091', '9801', 'a', '6645']
answer:
a, g, h, k, m, p, q, r, v


question:
['q', 'o', '1205', '4429', '6301', 'e', '2857', '5075', '5121', 'p', 'b', '5801', 'a', 'm', 'j', 'p', '1279', '7011', 'x', '2557', 'k', 'v', 'b', 'u', 'w', 'n', '1689', 'o', '1583', 'w', '6403', 'p', '6397', 'e', '823', '5699', 'd', '3399', 'd', 'b']
answer:
a, b, d, e, j, k, m, n, o, p, q, u, v, w, x


question:
['b', 'o', '9411', '9609', '1217', '2025', '7445', 'm', 'b', 'g', 'k', '6111', 'p', '1357', '2837', 'r', 'r', '4867', 'y', 'm', 'a', '1815', 'u', 'l', 'w', '4329', 'm', 'l', '7539', 'f', '9131', 't', 'h', '6449', '8287', 'x', 'o', 'p', '4597']
answer:

a, b, f, g, h, k, l, m, o, p, r, t, u, w, x, y