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: ['9877', 'm', 'r', '4177', '7697', 't', '8915', '4127', '6867', 'n', 'x', 'k', 'b', '5675', 'n', 'l', 'e', 'd', '6825', '3797', 'n', '4211', '1221', 't', '9633', 'b', '8163', 'g']
Student:
b, d, e, g, k, l, m, n, r, t, x