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:
['749', 'r', 'a', 's', 't', '5905', 'm', 'd', '8437', '4583']
answer:
a, d, m, r, s, t


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


question:
['w', '2579', 'z', '805', '8585', '8763', '1653', 'v', 'p', '2939', 't']
answer:

p, t, v, w, z