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.
One example: ['8129', 'a', '4245', 'y', 'm', 'a']
Solution is here: a, m, y
Explanation: Here, the unique alphabets in the list are 'a', 'y', and 'm', hence their sorted order is 'a, m, y'.

Now, solve this: ['3551', 'm', 'b', '4517', '4251', '6221', 's', 'z', 'b', 'p', '859', '1547', 'r', '8389', '5583', '5515', 's', 'd', '1999', 'e', '8955', 'z', 'j', '3001', 'k', 'r', 'c', 'u', 'k', '4779', 'f', '6637', '31', '6451', '8525', '547', '6025', 'z', '6069', 'f', 'o', 'd', 'u', '6461', '2737']
Solution:
b, c, d, e, f, j, k, m, o, p, r, s, u, z