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', 'D', 's', 'p', '3599', '7793', '2403', 'Y', 'a', 'u', 'Q']

15, 4, 19, 16, 3599, 7793, 2403, 25, 1, 21, 17