Detailed Instructions: 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.
Q: ['8975', '3427', '6001', '9323', 'k', 's', 'm', '103', '9535', 'x', '1279', '9917', 't', '6739', 'p', 'y', '2553', '6259']
A:
k, m, p, s, t, x, y