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: ['t', 'x', '1699', '8727']

SOLUTION: t, x

PROBLEM: ['u', '4731', 'l', 'p', '1997', '601', 'n', 'l', 'p', '211', '7355', '6537', 'w', 'x', '1741', '8145', '3689', 'm', 'y', '6945']

SOLUTION: l, m, n, p, u, w, x, y

PROBLEM: ['6551', '8731', 'p', 'l', '5207', 'c', 'p', 'l', 'f', '3875', 'o', '6363', '5647', 'i', '1093', '7057', '1975', 'l', '9783', 'v', '8391', '8935', '745', 'e', '411', '2741', 'r', '411', '5653', '1133', 'a', 's', '3739', 'p', 'g']

SOLUTION:
a, c, e, f, g, i, l, o, p, r, s, v