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: ['5971', 'x', 'c']

SOLUTION: c, x

PROBLEM: ['v', '5433', 'v', '6749', '7491', 'i', 'm', 'e', '5815', '8423', '833', '7359', 'm', 'i', 'f', 'u', 'p', 'j', 't', '3171', '6165', 'q', 'a', '9475', 'm', 'q', '5995', '8443']

SOLUTION: a, e, f, i, j, m, p, q, t, u, v

PROBLEM: ['8121', '7981', '3351', '7381', 'v', '1277', 'z', 'y', '9763', '8541', '6803', 't', 'd', 'h', '6363', '6717', '7075', '5429', '3663', '6797', '8861', '7573', 'y', '5191', 'r', '8657', 'f', 'a', '3677', '7093', 'r', '8437']

SOLUTION:
a, d, f, h, r, t, v, y, z