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: ['M', 'U', '2455', '1239', 'W', 'Y', 'i', '4421', 'U', '245', 'W']

13, 21, 2455, 1239, 23, 25, 9, 4421, 21, 245, 23