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 Input:
['m', '6761']

Ex Output:
m


Ex Input:
['p', '4329', '2437', '6279', 'u', '459', 'f', 'c', 'i', 'w', 'n', 't', '429', 'n', '73', '4995', 'p', 'z', '8459', '6133', 'y', 'r', '4057', 'a', '2717', '7803', 'r', 'm', '2879', '6989', '7223', 'v', '7929']

Ex Output:
a, c, f, i, m, n, p, r, t, u, v, w, y, z


Ex Input:
['4139', 'q', '7591', 'g', '5429', 'n', '7693', 'y', 'u', '1775', 'e', 'i', 'g', 's', 'a', 'z', 'g', 'v', '9111', 'f', 'u', 't', 't', 'u', '6185', '5133', '7425', '3105']

Ex Output:

a, e, f, g, i, n, q, s, t, u, v, y, z