Definition: In this task, you are given an input list A. You need to convert all the alphabets in the list with a number representing their position in the English alphabet. E.g., replace A by 1, B by 2, a by 1, b by 2, and so on.
Input: ['4375', 'L', '9789', 'P', 's', '5731', '6263', '4421', 'u', 'T', 'y', '1751', '4721', '8959', '6601', '4087', '833', '5529', '8429', 'o', 'O', 'a', 'p', 'C', '6585', '1581', 'b', '6439', 'O', 'u']

4375, 12, 9789, 16, 19, 5731, 6263, 4421, 21, 20, 25, 1751, 4721, 8959, 6601, 4087, 833, 5529, 8429, 15, 15, 1, 16, 3, 6585, 1581, 2, 6439, 15, 21