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: ['s', '6723', 'l', '1573', '1129', 'n', '4277', '5003', 'y', '7563', 'c', '6747', '3105', 's', '3593', '8417', '8253', '4157', 'w', 'f', 'z', 'd', '9685', '1033', 'h', '4893', 't', 'j', '6821', 'z', 'a', 'u', '591', 'o', '1087', '2147', '1223', '2339', 'i', 'y', '9307', 'x', 'z', 'r', 'y']

SOLUTION: a, c, d, f, h, i, j, l, n, o, r, s, t, u, w, x, y, z

PROBLEM: ['2161', '8009', '3057', 'r', '3897', 'd', 'j', '2727', 'b', '3231', 'i', '9227', '393', '5799']

SOLUTION: b, d, i, j, r

PROBLEM: ['l', 'k', '1265', '3433', 's', '6685', 'q', 'n', '5137', '75', 'e', '6311', '7645', 's', '8507', '3255', 'a', '2279', '7939', 'o', '749', 't', '8567', '2895']

SOLUTION:
a, e, k, l, n, o, q, s, t