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: ['N', '1509', 'k', 'i', 'S', '4231', 'I', '3807', 'a']

14, 1509, 11, 9, 19, 4231, 9, 3807, 1