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: ['O', 'm', 'Y', 'J', 'B', 'U', 'W', 'i', '7407', 'g', 'O', 'v', '9433', 'm', '4981', 'm']

15, 13, 25, 10, 2, 21, 23, 9, 7407, 7, 15, 22, 9433, 13, 4981, 13