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: ['w', 'g', '1649', 'a', '2115', '6763', 'r', 't', 'l', 's', 'y', '5659', 'a', 'b']

SOLUTION: a, b, g, l, r, s, t, w, y

PROBLEM: ['7073', 'd', 'e']

SOLUTION: d, e

PROBLEM: ['473', '4217', 'f', '7983', 'x', '1343', 'v', 'f', '8521', 'g', '9703', '6587', 'v', '1789', '8069', '8099', '993', 'a', '2219']

SOLUTION:
a, f, g, v, x