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: ['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: ['e', 'k', '7569', '6387', '4593', '2445', '345', '2905', 'h', '3119', '7001', 'x', 'a', '2943', '3635', 'l', 'q', 'z', 'g', '2657', '7849', 'i', '9413', 'm', 'e', '2951', 'd', '2963', 'b', 'u', 't', 'i', '1141', 'c', 'm', '8607', 's']

SOLUTION: a, b, c, d, e, g, h, i, k, l, m, q, s, t, u, x, z

PROBLEM: ['6555', 'e', '7985', 'j', 'd', '8133', 'f', 'y', 'u', '1875', 'e', '9639', 'd', 'n', 'd', 'v', 'o', 's', '7607', '7401', 'p', 'v', 'r', '4385', '4287', '2699', 'k', '1859', 'z', '839', 'm', '1897', '4287', 'f', '2429']

SOLUTION:
d, e, f, j, k, m, n, o, p, r, s, u, v, y, z