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: ['5961', 'u', '1503', 'O', '8967', '8247', 'a', '5013', '5437', '3911', '2409', 'M']

5961, 21, 1503, 15, 8967, 8247, 1, 5013, 5437, 3911, 2409, 13