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', '303', 'H', '1293', '2053', 'u']

15, 303, 8, 1293, 2053, 21