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: ['6737', 'g', '9985', '5257', 'k', 't', '7863', 'y', '8319', 'l', 'o', '6505', '6531', 'z', '3055', '2943', '3625', 'h', '4867']

SOLUTION: g, h, k, l, o, t, y, z

PROBLEM: ['9385', '4021', 'y', '9629', 'u', '7623', 'd', '5155', 'x', '2605', '8893', 'l', 'p', 'a', 'm', '6699', 'i', '4503', '6623', 'm', 'l', '6115', 'p', 'w', '9691', '811', '4769', '2659', 'x', 'c', '6513', '5499', 's', 'q', 'f', 'v', 'z', 'w', 'z', '1361']

SOLUTION: a, c, d, f, i, l, m, p, q, s, u, v, w, x, y, z

PROBLEM: ['c', '1445', '5549', 'u', '9615', 'g', '8279', 't', '9109', 'q', '3963', 'd', '7525', '2893', 'y', '831', 'o', '7345', 'a', 'e', 'z', '3413', 'k', 'c']

SOLUTION:
a, c, d, e, g, k, o, q, t, u, y, z