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:
['y', 'i', '257', '3695', 's', '6717', '4817', '4117']
answer:
i, s, y


question:
['t', 't', 'p', '3245', 'x', 'g', 'i', 'u', '2599', '8613', 't', 'v', 'p', '5635', 'y', '9567', '5193', '8617', 'q', 'f']
answer:
f, g, i, p, q, t, u, v, x, y


question:
['7197', '1017', 'w', 'j', 'y', 'z', 'f', '8477', '7219', 'l', 'a', 'b', '4141', '2335', 'z', 'g', 'q', 'g', '2583', 'w', 'q', '4557', 'y', '5391', 'a', 'l', '4495']
answer:

a, b, f, g, j, l, q, w, y, z