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:
['q', '6421', 'w', 'x', '669', 'h', '3853', '6609', 'p', '947', 'g', 'c', 'x', '2617', 'v', 'e', '4795', '5755', 'a', '2379', 'y', '5939', 'l', 'h', 'g', '3779', 'c', 'm', '3157', '4027', 'g', '2917', '9461', '7271', 't', 'i', '9807', '147']
answer:
a, c, e, g, h, i, l, m, p, q, t, v, w, x, y


question:
['5039', '2227', 't', 'o', '3313', 'm', 'v', '637', '6773', 'v', 'c', 'l', 'y', 'u', '3823', '9669', 'k', 'h', '3589', 'b', 'i', '3833', 's', 'm', '8201', 'u', '3143', 'k', '4111', '9769', '425', '4339', '209', 'c', 'c', '669', '8201', 'u', '7443', '2387', '6919', 'b', 'b', '2873']
answer:
b, c, h, i, k, l, m, o, s, t, u, v, y


question:
['8801', '9599', '4647', '517', '7807', '6381', 'f', 'u', 'z', 'i', 'v', 'b', 'e', 'q', 'm', '4283', 'o', 'k', 'm', 't', 'a', '5579', '1169', '1549', '9791', 'c', '7649', 'y', 'z', 'e', '7833', 'i', '869', 's', '5237', 'd', '5539', 'r', '261', '4693', 'o', 'f', 'l', '7013', '5649']
answer:

a, b, c, d, e, f, i, k, l, m, o, q, r, s, t, u, v, y, z