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: ['o', 'c', '6469', 'x', '8815', '4441', '6193', 'u', 'm', 'a', '9879', 'p', '8335', 'c', 'z']

SOLUTION: a, c, m, o, p, u, x, z

PROBLEM: ['9579', 'm', 'v', 'r']

SOLUTION: m, r, v

PROBLEM: ['t', 'o', 'o', 'd', 'k', 'k', 'i', '5497', '7517', 't', 'v', '7689', 'j', 'e', 'v', '1885', '2895', '2373', '9943', '7613', '1439', 't', 'm', 'e', '267', 'j', 'r', 'o', '8653', 'c', '4291', '5861', '4255', '4603', '4821', '9841', 'o', '847', 'b', 'a']

SOLUTION:
a, b, c, d, e, i, j, k, m, o, r, t, v