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: ['1989', '3539', 'n', '6145', '6791']

1989, 3539, 14, 6145, 6791