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:
['7965', '6465', 'c', '7963', 'j', '6839', '9989', '1019', 'x', '1303', '2633', 'y', '6865', 'a', 'k', '635', '3719', '7229', 'k', 't', 'r', '5741', '9569', '4931', '1125', 'f', '5429', 'c', '2065', '6315', 'e', '6877', '2005', 'x', '7831', '7297', 'm', '3571', 'b', '8617', '2981', 'i', '5105', 'g', 'u']
answer:
a, b, c, e, f, g, i, j, k, m, r, t, u, x, y


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


question:
['2259', '9785', 'c', 'j', 'n', '1799', 'j', 'u', 'x', '4273', '485', '5935', 'e', 'j', '2117', 'n', '7717', '1529', 'l', '3651', '9587', 'k', '5205', '5277']
answer:

c, e, j, k, l, n, u, x