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: ['S', '9871', '5623', 'H', 'j', '1839', 'O', 'u', '3225']

19, 9871, 5623, 8, 10, 1839, 15, 21, 3225