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: ['4041', 'l', 'g', '9571', '9295', '1395', 'l', 'p', 'f', 'w', 'g', '1721', '2421', 'w', 'z', '2235', 'p', '7851']

SOLUTION: f, g, l, p, w, z

PROBLEM: ['2161', '8009', '3057', 'r', '3897', 'd', 'j', '2727', 'b', '3231', 'i', '9227', '393', '5799']

SOLUTION: b, d, i, j, r

PROBLEM: ['1377', '7395', 'm', 'p', 'a', 'a', 't', 'p', '4759', '2997', 'a', '721', 'w', 'b', '161', '7781', '5185', 't', '3293', 'p', '8245', 'c']

SOLUTION:
a, b, c, m, p, t, w