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', '7519', 'G', 'Y', '837', 'U', '6707', 'Q', '8629', 'q', '1989', 'u']

15, 7519, 7, 25, 837, 21, 6707, 17, 8629, 17, 1989, 21