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:
['u', 'o', 'b', 'b', '5873', 'w', 'v', '4171', '7957', '3501', '2563', 'l', 'q']
answer:
b, l, o, q, u, v, w


question:
['5011', 'l', '925', 'e', 'b', '3077', 'm', '4541', '781']
answer:
b, e, l, m


question:
['g', 'i', '7221', '4541', 'x', 'c', 'a', 'j', 'c', 'c', 'b', '6301', '2595', 'f', '8335', '6133', 'n', 'c', '7751', '9393', '3501', '8675', 't', '5807', 'y', '147', '4809', 'b', '963', 'u', '3475', 'r', '9313', 'w', '737', 'q', '239', '1629', '3663']
answer:

a, b, c, f, g, i, j, n, q, r, t, u, w, x, y