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: ['H', 'u', '3459', '8447', 'M', 's', 'U', '5393', 'p']

8, 21, 3459, 8447, 13, 19, 21, 5393, 16