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: ['u', '4731', 'l', 'p', '1997', '601', 'n', 'l', 'p', '211', '7355', '6537', 'w', 'x', '1741', '8145', '3689', 'm', 'y', '6945']

SOLUTION: l, m, n, p, u, w, x, y

PROBLEM: ['a', '2579', 'f', '6787', '123', '225', '6499', '4419', 'o', '1785', '7981', 'z', 'b', '2441', '2821', 'o', 'k', '2747', 's', 'u', 'q', '3901', '7629', 'k', 'm', 'q', '6577']

SOLUTION: a, b, f, k, m, o, q, s, u, z

PROBLEM: ['5111', '1177', 'w', 'p', '2427', 't', '6117', 'q', '3857', 'g', '4731', '7059', '5421', '7937', '1293', '3775', 'n', 'l', '7411', 'u', '2165', 'p']

SOLUTION:
g, l, n, p, q, t, u, w