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: ['2799', '7519', '345', 'e', 'l', '9369', '4703', '4111']

SOLUTION: e, l

PROBLEM: ['l', 'o', 's', '7411', '7847', '2557', '1977', '2863', '2325', '4177', '4183', '4241', '1005', '1137', '1371', 'v', 'p', 'a', '2453', 'l', '6315', 'l', '6463', 'n', '7645', '9669', '5411', '1631', '5995', 'z', '227']

SOLUTION: a, l, n, o, p, s, v, z

PROBLEM: ['5571', '1769', '3203', 'c', '1593', '7127', 'l', 'o', '7077', 'q', '2399', '2449', '9389', '6313', '6315', 'f', 'd', '1575', '5931']

SOLUTION:
c, d, f, l, o, q