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: ['h', '6865', '4019', '8571', 'y', '5575', '7835', '9537', 'n', '875', 't', 'a', 's', '2769', 'p', '1607', 'n', '4087', '961', '7869', '5085', '2131', '4867', 'j', 'h', 'y', '3105', '6609', 's', 'l', '3399', '5013']

SOLUTION: a, h, j, l, n, p, s, t, y

PROBLEM: ['p', '6123', '6961', 't', 'p', 'h', '9035', 'r', '6341', 'x', '3635', '5885', 't', '3543', '9567', '1787', 'o', '2991', 'k', '3441', '4091', 'a', 'r', '423', '9383', '7147', 'h', '663', 'd']

SOLUTION: a, d, h, k, o, p, r, t, x

PROBLEM: ['7955', '8045', 'a', 't', 'y', '7173', '429', '3627', 'o', '691', '9181', '6333', 'd', 'z', '8251', 'l', '6153', '8903']

SOLUTION:
a, d, l, o, t, y, z