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: ['2697', 's', '8733', 'n', '5871', 'f']

SOLUTION: f, n, s

PROBLEM: ['8319', 'f', 'w', 'w', 'v', '6521', '4503', 'b', 's', 'b', '9651', 'k', '4635', '2195', '7537', '6839', 'i', 'd', 'b', '205', 'q', '7333', 'q', '5129', '4921', 's']

SOLUTION: b, d, f, i, k, q, s, v, w

PROBLEM: ['o', 'e', 's', '7907', 'x', 'w', 'r', '9469', 't', '2865', '8121', 'g', '8103', 'l']

SOLUTION:
e, g, l, o, r, s, t, w, x