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: ['U', '2911', '8401', '717', 'u', '1585', 'a', '3499', 'u']

21, 2911, 8401, 717, 21, 1585, 1, 3499, 21