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: ['d', '2359', '6571', 'c', 'n', 'u', '9513', '9321', '1689', 'b', '969', '1823', 'e', 'b', '9147', 's', '1811', 'k', '5443', '8699', '5483', 'v', 'w', 'n', '1215']

SOLUTION: b, c, d, e, k, n, s, u, v, w

PROBLEM: ['5553', 'f', '3881', '8867', 's', 'd', 'a', '375', '7889', '3949', '2905', 'w', 'q', 'q', 'd', '4203', 'i', '2601', 'y', 'p', 'k']

SOLUTION: a, d, f, i, k, p, q, s, w, y

PROBLEM: ['4079', 'c', '9165', 't', '7705', 'c', 'm', '2093', '5337', 'l', '1807', '6059', '8819', '2123', 'q', 's', 'm', 'q', 'f', '547', '8009', '3183', 'r', '1231', '627']

SOLUTION:
c, f, l, m, q, r, s, t