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: ['3901', '6917', '7815', 'G', '4135', 's', '2067', 'U', '9103', 'S', '9821', 'O', 'a', '1529', '6921', '979', 'P', '2277', '3333', '3015', '1721', 'G', 'k', '8533']

3901, 6917, 7815, 7, 4135, 19, 2067, 21, 9103, 19, 9821, 15, 1, 1529, 6921, 979, 16, 2277, 3333, 3015, 1721, 7, 11, 8533