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:
['o', '5503', '5837', '4539', '7631', 'm', '2641', 'p', '7901', '8117', 'z', '3373', '3215', 'v', 'a', '5949', 'w', '9049', 'd', 'a', 'l', 'v', 'l', 'n', 'w', 'r', 'j', '9031', '9609', '4209', 'c', '7453', '5855', '2883', '5941', 't', '4283', 'x', 'x', 'n', 'c']
answer:
a, c, d, j, l, m, n, o, p, r, t, v, w, x, z


question:
['3797', '6117', 'x']
answer:
x


question:
['1473', '5161', 'z', 'c', 'h', '5227', '3573', 'x', 'e', 'r', 't', 'g', 'p', 'e', '641', 'o', '213', 'y', 'm', '2431', 'k', '229', 'n', 'a', '5937']
answer:

a, c, e, g, h, k, m, n, o, p, r, t, x, y, z