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:
['1707', '381', '3957', '7853', '4987']
answer:
-1


question:
['r', 'n', '7583', '8697', '7927', 'l', '5003', '1363', 'p', 'e', 'q', '6227', '6915', '8619', '9011', 'n', '3063', '3799']
answer:
e, l, n, p, q, r


question:
['1687', '6923', 'c', 's', '5951', 'm', 'l', 'r', 'c', '4245', '8927', 't', '7907', '2971', '4331', '8703', '6851', 'b', '3399', '9149', '7835', 'q', 'z']
answer:

b, c, l, m, q, r, s, t, z