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: ['5091', 'z', '1255', 'r', 'u', 'x', '3177', 'f', 's', 'a', 'f', '2563', 'w', '8311', '8197', '1819', '3615', '539', 'i', '3425', 'k', '2437', 'h', '7929', 'u', '7417', '2541', 'u', '3073', '3347', '5591', '9839', 'q', '2551', '921', '6187', '9825']
Student:
a, f, h, i, k, q, r, s, u, w, x, z