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:
['4009', 'y', '9077', 'p', 'q', '6711', '6443', '5491']
answer:
p, q, y


question:
['6955', '721', '2763', '8121', '9109', '6341', 'p', 't', 'x', '6963', '1137', 'z', 'u', '1949', '7029', 't', '9539', 'a', 'u', '1873']
answer:
a, p, t, u, x, z


question:
['4457', 'f', '5753', 'v', '5957', 'm', '47', 'w', '195', '4321', 'u', '1433', '3935', 'a', '7307', '8517', 'v', 't', '4061', 'h', 'z']
answer:

a, f, h, m, t, u, v, w, z