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.
One example: ['8129', 'a', '4245', 'y', 'm', 'a']
Solution is here: a, m, y
Explanation: Here, the unique alphabets in the list are 'a', 'y', and 'm', hence their sorted order is 'a, m, y'.

Now, solve this: ['463', 'x', 'z', 'y', 'n', 'g', '5973', '2771', '773', 'e', '7507', 'z', '9493', 'q', 'v', 'g', 'r', '7615', '9497', 't', 'l', '5379', 's', '4431', 'b', '8259', '2269', 'f', 't', '1957', '5521', 'c', 'f', 'd', '4807', '4525', 'n', 'y', 'u', '5515', '8129']
Solution:
b, c, d, e, f, g, l, n, q, r, s, t, u, v, x, y, z