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: ['7065', 'q', 't', '3177', '9035', 'i', 'l', 'd', '8961', '1183', '6507', 'u', 'c', 't', '2467', '7659', 'e', '8963', 'j', 'g', 'p', '6779', '7115']

SOLUTION: c, d, e, g, i, j, l, p, q, t, u

PROBLEM: ['6955', '721', '2763', '8121', '9109', '6341', 'p', 't', 'x', '6963', '1137', 'z', 'u', '1949', '7029', 't', '9539', 'a', 'u', '1873']

SOLUTION: a, p, t, u, x, z

PROBLEM: ['4111', 'm', 'l', 'b', 'q', 'b', 'w', '471', 't', 'p', '2561', '3367', 's', '2047', '3165', '459', '7949', '7403', 'a', '4761']

SOLUTION:
a, b, l, m, p, q, s, t, w