Teacher: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.
Teacher: Now, understand the problem? Solve this instance: ['3923', 'p', '8557', '3013', '1753', '7045', '6185', '6989', '5725', 't', '493', 's', 'i', '6383', 't', 'r', '1997', 'n', '7609', '1939', 'g', '6489', 'k', 'q', 'w', '8365', '4465', '315']
Student:
g, i, k, n, p, q, r, s, t, w