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 is below.
Q: ['8129', 'a', '4245', 'y', 'm', 'a']
A: a, m, y
Rationale: Here, the unique alphabets in the list are 'a', 'y', and 'm', hence their sorted order is 'a, m, y'.
Q: ['7411', '9671', '6773', '8409', '6589', '9017', '3175', '7691', 'u', '8065', '2275', '1951', '7519', '2635', '7767', '1933', '6869', '2929', 'n', 'a', '9523', '517', '7221', 'n', 's', '7561', 'c', 't', 'z']
A:
a, c, n, s, t, u, z