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: ['9573', '8607', 'v', '8399', '4371', '7033', 'd', 'b', '1099', 'w', '7869', 'p', '7313', '8415', '2889', 'a', 'n', '5735', '1177', '5839', 'z', 'w', 'c', 'd', 'a', 'n', 'y', 't', '6053', '9301', '8939', '3737', 'k', 'n', '6475', '4155', '4367', 'l', 's', '5347', '7659', 'b']
Student:
a, b, c, d, k, l, n, p, s, t, v, w, y, z