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: ['X', '9503', '5671', 'p', '3921', '6341', 'F', 'k', '3521', 'a', 'S']

24, 9503, 5671, 16, 3921, 6341, 6, 11, 3521, 1, 19