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: ['6589', 'S', 'e', '653', '6121', 'a', 'u', 'R', 'b', 'O', 'X', 't', 'u', 'H', 'j']

6589, 19, 5, 653, 6121, 1, 21, 18, 2, 15, 24, 20, 21, 8, 10