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: ['6441', '8897', 'S', 'u', 'P', '4207', '8405', '1265', 'u', 'D', '6635']

6441, 8897, 19, 21, 16, 4207, 8405, 1265, 21, 4, 6635