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:
['815', '6967', '6553', 'r', 'y', '3641', 'q', 'b', '6131', '4289', 'w', '6093', '6055', 'i', 'b', 'y', '5107', 'v', 'g', '9709', 'x', 'i']
answer:
b, g, i, q, r, v, w, x, y


question:
['1449', 'a', '6261', '303', '4651', 'n', 'u', '1595']
answer:
a, n, u


question:
['6429', 'm', '6509', '1527', 's', 'q', 'j']
answer:

j, m, q, s