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: ['Y', '3101', '9483', 'T', 'z', 'u', 'W', '6501', 'm', 'Y', '495', '663', 'S', 'L', '251', 'U']

25, 3101, 9483, 20, 26, 21, 23, 6501, 13, 25, 495, 663, 19, 12, 251, 21