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: ['5345', 'f', '6605', 's', 'q', 'w', 'p', 'o', 's', 'u', 'i', '7339', '8379', 'h', '9547', 'b']

SOLUTION: b, f, h, i, o, p, q, s, u, w

PROBLEM: ['2381', 'y', '6631', '5839', 'r', 'm', 'z', 'b', '4663', '595', '7771', '5305', '5087', '3317', '3125', '9551', '4343', '5121', 'm', 'i', '131', '8401', '5379', '1775', 'u', '1125', '9793', '4123', 'h', '1613']

SOLUTION: b, h, i, m, r, u, y, z

PROBLEM: ['7969', '673', '3833', 'a', '7279', '2201', 'c', '6475', '4447', '4341', 'k', 'u', 'n', 'k', '8333', 'a', 't', '7343', 'o', 'a', '879', '503']

SOLUTION:
a, c, k, n, o, t, u