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: ['6737', 'g', '9985', '5257', 'k', 't', '7863', 'y', '8319', 'l', 'o', '6505', '6531', 'z', '3055', '2943', '3625', 'h', '4867']

SOLUTION: g, h, k, l, o, t, y, z

PROBLEM: ['s', '2507', '3091', 'g', '7643', '2573', 'w', 'r', '1977', 'q', 'c', 'j', '1335', '9671', '7317', '567', '2041', '5777', 'w', 'm']

SOLUTION: c, g, j, m, q, r, s, w

PROBLEM: ['y', 'n', '6611', 'y', 'l', '4965', '8101', '8803', '7681', 'i', '4611', '1371', 'q', '741', '5929', 'b', 'b', 'b', 'u', 'g', '9639', 'a', '8741', '4889', '2707', '1983', 'o', 'l', 'c', '4587', '3893', '769', 'i', '3163', 'i', 'z', '621', 'a', '2231', 'h', '5119', 'c', '4973', '6521']

SOLUTION:
a, b, c, g, h, i, l, n, o, q, u, y, z