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: ['1971', 'g', 't', 't', 'x', 'q', 'o', 'm', 'h', '9481', '1729', '5527', 'u', '3157', 's', '8795', 'z', 'g', 'i', '1649', 'p', '65', 's', 'u', '6843', 'r', 'l', 'k', 'n', 's', 'm', '7991', 'u', 'a']

SOLUTION: a, g, h, i, k, l, m, n, o, p, q, r, s, t, u, x, z

PROBLEM: ['6143', '9073', 'h', '1459', 'q', '5799', '6555', '525', '7921', '5041', '3273', '383', 'd', '9075']

SOLUTION: d, h, q

PROBLEM: ['461', 'd', '8697', 't', '6025', 'u', 's', 'j', '1627', '2299', 'r', '2507', '8213', '1975', '45', '9079', '531', 'd', 'r', 'd', 'z', 'a', '9147', 'j', '1375', '3325', '6269', 'f', 'e', 'c', '463', 'd', '8845', '1597', '3309']

SOLUTION:
a, c, d, e, f, j, r, s, t, u, z