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:
['749', 'r', 'a', 's', 't', '5905', 'm', 'd', '8437', '4583']
answer:
a, d, m, r, s, t


question:
['x', 'i', 'r', '6011', 't', 'f', 'b', 'i', '8367', '4051', '1459', 'f', '5583', '9609', 'l', 'q', 'g', '8443', 'o', '8697', '7053', '8325', 'k', '7021', 'q', 'm', '6899', '9981', '8985', 'i', 'j', '8043', 'k', '535', '7603', '7629', 'k', '2779', 'g', '2049', 'x', 'd', '8527', 'k', 'q']
answer:
b, d, f, g, i, j, k, l, m, o, q, r, t, x


question:
['9789', 's', 'h', 'n', '61', '931', '2279', '2577']
answer:

h, n, s