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.

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

[EX Q]: ['2799', '7519', '345', 'e', 'l', '9369', '4703', '4111']
[EX A]: e, l

[EX Q]: ['7631', 'a', 'o', '7727', '9835', '5615', '1807', 'i', 'd', 'y', '2339', '7245', '9629', '1885', 't', '7787', '2611', '3667', '3577']
[EX A]:
a, d, i, o, t, y