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: ['c', '1693', 'l', 'u', 'x', '3609', 'h', '4159']

SOLUTION: c, h, l, u, x

PROBLEM: ['8051', 'h', 'g', 's', 't', 'p', 'w', 'x', 's', '8521', 'm', '9719', 'j', 'n', 'i']

SOLUTION: g, h, i, j, m, n, p, s, t, w, x

PROBLEM: ['6917', 't', 'g', '9881', 'r', '8743', '1989', '9751']

SOLUTION:
g, r, t