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: ['s', 'u']

SOLUTION: s, u

PROBLEM: ['o', 'c', '6469', 'x', '8815', '4441', '6193', 'u', 'm', 'a', '9879', 'p', '8335', 'c', 'z']

SOLUTION: a, c, m, o, p, u, x, z

PROBLEM: ['9677', '9087', 'x', 'j', '2865', '9737', '8917', '3865', '4067', '5759', 'j', '5527', '1583', '4535', 'x', 'o', '5541', '1601', '161', '9539', '3247', '6527', 'w', 'c', '1231', '691', '6173']

SOLUTION:
c, j, o, w, x