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: ['7515', 'q', '7213', '87', '6777', 'D', 'G', '9745', 's', 'c', 'w', 'R', 'c', '2143', '2537', 'U', 'j', '3013', 'E', 'B', '5139']

7515, 17, 7213, 87, 6777, 4, 7, 9745, 19, 3, 23, 18, 3, 2143, 2537, 21, 10, 3013, 5, 2, 5139