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: ['u', '4731', 'l', 'p', '1997', '601', 'n', 'l', 'p', '211', '7355', '6537', 'w', 'x', '1741', '8145', '3689', 'm', 'y', '6945']

SOLUTION: l, m, n, p, u, w, x, y

PROBLEM: ['3223', 'h', 'w', 'f', 'y', '1667', '8843', '8759', '9203', '3305', '3549', '5507', '6251', 't', '8319', '9121', '6643', 'u', '4273', '4429', '7543', '7909', '789', '9183', '5729', 'd', '7063', 'b', '6677', 'w', 'x', 'x', 'z', '769', 'p', 'd', 'h']

SOLUTION: b, d, f, h, p, t, u, w, x, y, z

PROBLEM: ['5867', 'c', '5995', 'f', '3323', '9903', 's', '1647', 'q', 's', '4213', '4401', 'w', '785', 'h', '3829', '931', '1901', '3943', '9683', '7809', 'k', '3121', '9383', 'f', 'r', 'y', 'l', '7547', '6353', 't', '5197', 'n', '1709']

SOLUTION:
c, f, h, k, l, n, q, r, s, t, w, y