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: ['1367', 'h', '4153', '1587', 'h', 'b', 'n', 'u', 'n']

SOLUTION: b, h, n, u

PROBLEM: ['4905', 'w', '3143', '2217', '573', '1073', '63', 'a', '3971', '2887', '3485', 'y', '3893', '1059', '7623', 'x', 'd', '2991', 'e', 's', '735', 'm', 's', '257', 'x', '5559', '97', 'p', '7237', '693', '7229', 'd', '2311', '807', 'd', 'l', '1247', 'l', '359']

SOLUTION: a, d, e, l, m, p, s, w, x, y

PROBLEM: ['7965', '6465', 'c', '7963', 'j', '6839', '9989', '1019', 'x', '1303', '2633', 'y', '6865', 'a', 'k', '635', '3719', '7229', 'k', 't', 'r', '5741', '9569', '4931', '1125', 'f', '5429', 'c', '2065', '6315', 'e', '6877', '2005', 'x', '7831', '7297', 'm', '3571', 'b', '8617', '2981', 'i', '5105', 'g', 'u']

SOLUTION:
a, b, c, e, f, g, i, j, k, m, r, t, u, x, y