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.

['4749', '4607', '625', '6907', 't', 'b', '8479', '6505', 'r']
b, r, t

['5011', 'l', '925', 'e', 'b', '3077', 'm', '4541', '781']
b, e, l, m

['v', 'r', '2343', '2539', 'f', 'w', 'y', 'w', 'l', '5915', 'g', '413', 'z', 's', 'o', 'u', '3925', '8831', 'v', '5795', 'o', '1385', '1993', 'z', 'l', '7029', '1691', '7887', '4161', 'q', 'n', 'v', 'b', '7733', 'j', '1275', '7129']

b, f, g, j, l, n, o, q, r, s, u, v, w, y, z