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: ['5921', '5481', 'T', 'B', '9333', 'S', 'M', 'I', 'n', 'P', 'U', '4463', '4233', '343', '6473', '2101']

5921, 5481, 20, 2, 9333, 19, 13, 9, 14, 16, 21, 4463, 4233, 343, 6473, 2101