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.

[Q]: ['6955', '721', '2763', '8121', '9109', '6341', 'p', 't', 'x', '6963', '1137', 'z', 'u', '1949', '7029', 't', '9539', 'a', 'u', '1873']
[A]: a, p, t, u, x, z


[Q]: ['5971', 'x', 'c']
[A]: c, x


[Q]: ['2409', 'p', '7623', '3313', '8507', 'o', '3247', 't', 'f', '4875', 'k', '3549', '1183', '9653', '2181', 'd', 'f', 'f', '4019', 'x', '6045', 'x', '5581', '8329']
[A]:
d, f, k, o, p, t, x