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: ['r', '507', '2983', '5121', '2791', '3241', 't', '7559', '9585', '1473', '6047', 'l', '7389', '1975', 'd', 'k', 'i', '8039', '8663', '455', '3623', 's', '9685', '3713', 'g', 'x', 'o', 'p']
Student:
d, g, i, k, l, o, p, r, s, t, x