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:
['4041', 'l', 'g', '9571', '9295', '1395', 'l', 'p', 'f', 'w', 'g', '1721', '2421', 'w', 'z', '2235', 'p', '7851']
answer:
f, g, l, p, w, z


question:
['a', 'a', 'b']
answer:
a, b


question:
['r', '2347', 'e', 'j', '1437', '5135', '7975', 'w', 't', 'k', '6035', 'e', '5603', 's', 'h', '3547', 'f', 'c', 'w', 'b', 'b', '475', 'x', '6777', 'g', '5103', '125', '8375', 'y', '329', '2381', '9765', 'a', '7169', 'd', 'x']
answer:

a, b, c, d, e, f, g, h, j, k, r, s, t, w, x, y