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', 'r', '7769', '2159', 's', '3269', '5527', 'l', 'z', 'e', '5165', 'x', 'x', '8273', 'g', 'm', '7609', '4015', '6403', '3753', 'y', 'h', 'l', 'i', '389', 'm', 'u', '6845', 'r', 'c', '7571', '3355', '9755', 'n', '4625', 'p', '5645', '1703', '4439', 't', '8431']

SOLUTION: c, d, e, g, h, i, l, m, n, p, r, s, t, u, x, y, z

PROBLEM: ['q', 'h', 'q', '7185', 'f', 'l', 'r', '3605', 'x', 'i', 'v', '8789', 'u', 'x', 'x', '8315', 'x', 't', 'h', 'o', '4943', '5827', '7677']

SOLUTION: f, h, i, l, o, q, r, t, u, v, x

PROBLEM: ['7851', '1951', '1807', 'x', '1757', '5879', 'r', 'x', '9535', 'm', 'r', 'v', '8175', 'b', 'f', 'd', 'b', '9467', 't', '787', 'm', 'd', '2557', '7503', '4371', 'p', 'a', 'i', 'z', '6435', 'z', 'f', '4585', '6197', '9821', 'r', 'y', 'z', '2967', '3859', '2863', 'l', 's']

SOLUTION:
a, b, d, f, i, l, m, p, r, s, t, v, x, y, z