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:
['c', '7039', 'g', '1899', 'r', '507', 'c', '2587', '3865', '1729', '3927', 'r', '3535', '2791', 'm', 'l', 'r']
answer:
c, g, l, m, r


question:
['d', 'p', 'q', '5319', 'w', '4887', '6695', 't', '7711', 'l', '7597', 's', 'n', '1461', 'e', '9045', '1307', 'j']
answer:
d, e, j, l, n, p, q, s, t, w


question:
['7913', '4827', 'a', 'a', '3519', 'c', 'f', 'i', '6215', 'b', '2133', 'k', 'a', 'm', 'p', '6897', '3763', 'w', 'j', '6183', '469', '4045', 's', 'u', '2689', 'e', '6221', '4937', 'r', 'c', '5571', '1337']
answer:

a, b, c, e, f, i, j, k, m, p, r, s, u, w