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: ['2915', '6033', '5541', '4685', '1263', '6701', 's', '7269', 'g', '8033', '8171', '6917', 'l', '2913', '447', 'g', 'a', 'z', 'o', '7563', '5385', '5259', '5067', '4869', '2653', '6925', '7001', '8553', 'x', '1243', '9131', '5037']

SOLUTION: a, g, l, o, s, x, z

PROBLEM: ['o', 'c', '6469', 'x', '8815', '4441', '6193', 'u', 'm', 'a', '9879', 'p', '8335', 'c', 'z']

SOLUTION: a, c, m, o, p, u, x, z

PROBLEM: ['m', '2547', 'x', 'y', 't', '2135', '9021', 'v', '9589', 'u', '503', 'v', '2251', 'g', 's', 'd', '9541', 'x', '8345', '9807', '4399', 'g', 'z', '5295', 's', 'i', '1723', '6247', 'w', 'f']

SOLUTION:
d, f, g, i, m, s, t, u, v, w, x, y, z