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:
['315', '9975', '3013', 's', '6131', 'e', 'e', 'u', 'a', '1729', 'g', 't', 'y', 'f', '7523', 'e', 'g', '489', 'm', 'p', 'f', 'e', '2077', 'e', 'g', 'c', 'l', '6389', 'k', 'b']
answer:
a, b, c, e, f, g, k, l, m, p, s, t, u, y


question:
['y', '8115', 'f', '5333', 'f', '3437', 'b', 'e', '5719', 'm', 'w', '95', '4863', 'k', '4895', 'a', '8179', 'm', '7919', '1731', '229', 'r', '1847', '7559', '6669']
answer:
a, b, e, f, k, m, r, w, y


question:
['5619', '1307', '37', 'e', 'o', 'q', 'p', '7549', '8827', 'n', 'l', '5069', 'f', '8673', 'r', 'h', '9003', 'c', '6735', '5263', 'x', '1225', 'b', 'q']
answer:

b, c, e, f, h, l, n, o, p, q, r, x