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:
['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:
['y', 'b', 'r', 'f', '3745', 'n', '2921', '8133', 'r']
answer:
b, f, n, r, y


question:
['x', '177', 'w', 't', '197', 'f', '605', 't', 'h', 'k', 'q', 'h', '3277', '7423', 'o', '7801', '5375', '861', '8467', '9501', 'y', 'k', '291', 'p', '9891', '7421', 'k', 'v', 'o', 'q', 'j', '6123', 'x', 'g', 'r']
answer:

f, g, h, j, k, o, p, q, r, t, v, w, x, y