TASK DEFINITION: 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.
PROBLEM: ['9689', '9727', 't', 'd', '2103', 'c', 'n', '8553', '4559', '7815', 'u', 'l', 'c', 'e', 'u', 'n', '7207', '4875', '7699', 'h']

SOLUTION: c, d, e, h, l, n, t, u

PROBLEM: ['4637', 'f', '2639', '8623', 'w', 'e', 'k', '5503', 'x', '6633', '7553', '1455', 'u', '1773', 'r', 'u', '1489', 'u', '1303', '9683', 'z', '565', '7041', 'x', 'z', '9431', 'k', 'v', 'j', 'z', '5469', '5665', '4089', '4951', '8263', '5675', '4095', '7745', 'z', '2437', 'd', 'e', 'w']

SOLUTION: d, e, f, j, k, r, u, v, w, x, z

PROBLEM: ['9839', 'm', '5121', 'y', 'j', 'b', '6675', 'o', 'c', '8399', '3873', 'o', '3935', '7611', 'l', 's', 'n', '5567', 'b', '1233', 'e', '3661', 's', 't', '4959', 'j', 'l', 'v', 'b', 'g', '685', 'v', '3733', 'w', '6327']

SOLUTION:
b, c, e, g, j, l, m, n, o, s, t, v, w, y