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:
['c', 'e', '6509', '1295', 'u', '5445', '1731', '3049']
answer:
c, e, u


question:
['u', '8229', '2731', '6595', '4675', 'n', 'a', '7361', '7401', '7273', 'b', '279', '5539', '7919', 'j', 'x', '9521', '8837', '7391', 'h', 'x', 'h', '7283', 't', '3769', '2317', '9131', 'h', 'y', 'c', '1625', 'm', 'e', 'a', '8437', '7543', 'p', '2451', 'k', 'r']
answer:
a, b, c, e, h, j, k, m, n, p, r, t, u, x, y


question:
['w', 'v', '7469', '6463', 'r', '2079', 'z', '55', 'x', 'a', 'g', '7363', '1081', 'k', 'g', 'h', '4071']
answer:

a, g, h, k, r, v, w, x, z