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: ['2521', '8027', 'm', '193', '615', 'l', '1947', '5949', '6307', 'r', '1015', '743', 'v', '6949', 'b', 'g', '8841', 'c', 'b', '2879']

SOLUTION: b, c, g, l, m, r, v

PROBLEM: ['575', 'u', 'c', '8113', '2853', '3661', '9427', '3071', '4069', '835', 'w', 't', 'w', 't', 'v', 'g', 'c', '5497', '1703', '8433', 'g', '3545', '2887', 'z', 'a', '2241', '5799', '5915', 'u', '4015', '8327', 'z', 'a', 'w', '8311', '289', '8575', 't', 'b', '2873', 'r', 'z', 'x', '1165', '9881']

SOLUTION: a, b, c, g, r, t, u, v, w, x, z

PROBLEM: ['f', 't', '1395', '4541', '7107', '4515', '3129', '3441', 'z', '9741', 'd', 'x', 'm', 'b', 'v', '4161', '3531', 'h', 'l', 'w', 'o', 'n', '3313', 'c', 'z', 'y', '4539', '3613', '8979', 'd', 'b', 'n', '4165', '9215', '6901', 'u', '1479', '3071', 'w', '2349']

SOLUTION:
b, c, d, f, h, l, m, n, o, t, u, v, w, x, y, z