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: ['m', '6537', '4063', '6413', 'k', 'd', '2479', 'p', '2251', 'q', '7079', 'r', 'd', 'p', '3347', '1391', '9847', '4487', 'u', '6951', '5285', '5837', '6747', 'r', 's', 'c', 'x', 'b', 'q', 'y', 'd', '331', '679', 'v', '1919', 'f', 'p', '1267', '3151']

SOLUTION: b, c, d, f, k, m, p, q, r, s, u, v, x, y

PROBLEM: ['y', 'b', 'r', 'f', '3745', 'n', '2921', '8133', 'r']

SOLUTION: b, f, n, r, y

PROBLEM: ['2137', 'i', '5893', '7417', 'p', '6715', 'u', '1657', '5781', 't', 'e', 'd', 'i', 'c', 'c', '1269', '1045', 'p', 'x', 'z', 'j', '6027', '2159', 'd', 'o', 'm', 'n', 'e', '9667', '2741', '5219', 'x', '459', 'a', '9389', 'l', 'f', '789', 'y', 'p']

SOLUTION:
a, c, d, e, f, i, j, l, m, n, o, p, t, u, x, y, z