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: ['9923', 'x', '1901', 'v', '1459', '7503', '3829', '4929', 'k', 'c', '3329', '8793', 'n', 'a', '7249', 'b', 'l', 'l', 'm', 'p', 'b', 'a']

SOLUTION: a, b, c, k, l, m, n, p, v, x

PROBLEM: ['t', 'x', '1699', '8727']

SOLUTION: t, x

PROBLEM: ['t', '8209', 'd', 's', 'c', '3939', 'k', 'u', 'q', 'y', 'x', 'q', '9753', 'y', '8915', '4263', 'i', '1717', '6511', 'h', 'q', 'p', '4217', '6051', 'p']

SOLUTION:
c, d, h, i, k, p, q, s, t, u, x, y