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.

['m', '7807', 'n', 'w', '5097', '1023', '2723', 'u', '3055', '7285', 'f', 'm', 'w', '5197', '9743', '7519', '4451', 'c', 't', '1939', '5847']
c, f, m, n, t, u, w

['4641', '2881', 'c', '4827']
c

['4667', '7785', 'm', '2013', '1515', 'u', '1425', '2671', 'b', 'f', '9803', 'x', '6249', '6437', 'z', '7133', 'b', 'a', 'o', '5629', 'z', '113', '1551', '6335', '523', 'q', 'u', 'i', '4865', 'v', 'c', 'q']

a, b, c, f, i, m, o, q, u, v, x, z