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: ['D', 'S', '6899', '9055', '5653', 'C', 'y', 'C', 'H', 'w', 'g', '9085', 'x', '9407', '843', 'Z', 'L', '3991']

4, 19, 6899, 9055, 5653, 3, 25, 3, 8, 23, 7, 9085, 24, 9407, 843, 26, 12, 3991