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: ['2459', '3709', 'f', '8673', '9313', 'm', 'd', 'g', 'c', 'g', 'u', 'f', 'p', 'i', '8771', '3613', '9669', '6221', '1211', '8331', '2295', 'b', 'f', 'm', '1377', '9831', '1751', 'k', '4831', 'm', '2747', '3435', '4543', 'c', '1729', 'e', '7093', '397', 'm', '383', '2019']

SOLUTION: b, c, d, e, f, g, i, k, m, p, u

PROBLEM: ['g', 'u', 'q', '1375', '9491', 't', 'w', 'c', 'v', 'y', '3169', '1607']

SOLUTION: c, g, q, t, u, v, w, y

PROBLEM: ['781', '8563', 'c', 'f', '7491', 'y', 'y', 'h', '2421', '3867', '1613', 'w', 'v', 'p', 'p', 'u', 'p', 'q', '597', '5701', 'g', 's', 'a', '9389', 'q', 'd', 'd', 'm', '8243', '3451', 't', 'x', '7179', 'x', 'b', '6443', '4015', 'l']

SOLUTION:
a, b, c, d, f, g, h, l, m, p, q, s, t, u, v, w, x, y