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: ['7013', '8755', 'u', '9377', 'n', '6997', '507', '8557', '9745', 'g', '3019', '93', 'l', '1219', 'a', '393', '2573', 'q', 'b', '6101', 'e']

SOLUTION: a, b, e, g, l, n, q, u

PROBLEM: ['o', '1099', 'r', '8995', 'o', '2909']

SOLUTION: o, r

PROBLEM: ['2047', 's', '9993']

SOLUTION:
s