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:
['9271', '6393', '6005', 'x', '2301', '3999', 'p', 'z', 'j', '1033', '7555', 'r', 'r', 'y', '8917', '5939', '4031', 'e', '8095', 'g', '6095', 'a', '4133', '6471', '2129', '8021', '1093', 't', '8805', '545', 'k', '3249', 'l', '1561', '9909', 's', '1963', 'o']
answer:
a, e, g, j, k, l, o, p, r, s, t, x, y, z


question:
['1979', 'b', 't', '1101', '7953', '2451', '7539', '6833', 'u', '49']
answer:
b, t, u


question:
['x', 'e', 'c', 'i', '8931', '3243', '2541', '4091', 'j', '3951', 'i', '1767', 'o', '6763', 'a', 'f', '7221', 'k', 'q', '8633', '2339', '5037', 'u', 'j', 't', '3241', 'z', '7431', 'i', 'i', '9481', '9935', 's', '6649', 'a', 'v', 'n']
answer:

a, c, e, f, i, j, k, n, o, q, s, t, u, v, x, z