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:
['d', '771', '4193', 'e', '1537', 'a', 'q']
answer:
a, d, e, q


question:
['c', '1693', 'l', 'u', 'x', '3609', 'h', '4159']
answer:
c, h, l, u, x


question:
['f', 'b', '1235', 'y', '9039', 'r', '9177', 'z', '1479', 'y', 't', 'j', 'p', 'h', '1873', 'c', 's', '6259', 'h', '4909', '2957', '6989', '9809', 'm', 'w', 'c', 'c', 'f', '8339', 'p', 'l', 'x', '7857', '2491', 'u', '3757', '9313', 'f', '3819', 'k', '8611']
answer:

b, c, f, h, j, k, l, m, p, r, s, t, u, w, x, y, z