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:
['6143', 'y', '5505', '9813', 'r', 'v', 'u', '8681', '2387', 'u', 'o', 'm', '9793', 'm']
answer:
m, o, r, u, v, y


question:
['5957', 'd', 'i', 'b', 'e', '5565', 'c', 'i', '2919']
answer:
b, c, d, e, i


question:
['b', 'g', 'r', '895', 't', 'v', 'x', '9413', 'g', 'r', 'g', 'u', '3131', '9153', '3065', '7777', '7789', '1783', '7895', '2855', '3531', '7587', 'x', '2965', 't']
answer:

b, g, r, t, u, v, x