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: ['999', 'b', 'C', '7987', 'b', 'p', '9743', '9955', '3105', 'Y', '9311', '775', '5995', '3243', '9773', '9107', '909', 'p', 'o', '1861', 'f', '4459', 'U', 'u', 's', 'R', 'O', '3337', 'I', '8825', '7885', 'Y', 'C', 'p', '5495', 'K', 'V', 'y']

999, 2, 3, 7987, 2, 16, 9743, 9955, 3105, 25, 9311, 775, 5995, 3243, 9773, 9107, 909, 16, 15, 1861, 6, 4459, 21, 21, 19, 18, 15, 3337, 9, 8825, 7885, 25, 3, 16, 5495, 11, 22, 25