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:
['1233', '405', '8901', '7147', '8841', 's', 'v', '3131', 'p', 'd', 'y', '5873', '439']
answer:
d, p, s, v, y


question:
['y', 'g', '107', '4899', '6357', '9777', 'k', '1865', '7029', 'q', 'x', '7051', 's', '6125', '4285', '2731', 'z', 'a', '737', '6137']
answer:
a, g, k, q, s, x, y, z


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