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:
['w', '6291', '3939', '9569', 'u', '1635', '3359', '8335', 'n', '2799', '7359', 'k', 'm', '2817']
answer:
k, m, n, u, w


question:
['o', '4169', 'k', '7349', 'w', 't', '8271', '8781', '3725', '2865', '6053', 'j', 'z', '4211', '8231', '213', '6389', 'f', 'h', 'g', '9269', '4617', '4137', 'i', 'y', 'i', 'n', '4597', 'p', 'z', '3195', '3231', 'c', '1901', '1231', 'p', '4509', '2557', '3715']
answer:
c, f, g, h, i, j, k, n, o, p, t, w, y, z


question:
['4749', 'd', 'l', 'c', 'k', 'p', '8791', 'd', '5669', 'n', 'z', '1355', '5401', '9315', '4337', '9729', '3121', 'm', '2781', 'n', '6803', '6129', '235', 'f', 'y', '6375', '2107', '8481', 'l', '3169', '1065', 'p', '5401', 'm']
answer:

c, d, f, k, l, m, n, p, y, z