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: ['t', '8513', 'U', '7631', '2981', '9435', 'B', '6279', 'B', '2199', 'g', 'I', '1669', '2957', 'o', 'M', 'q', 'p', 'k', 'q', '3147']

20, 8513, 21, 7631, 2981, 9435, 2, 6279, 2, 2199, 7, 9, 1669, 2957, 15, 13, 17, 16, 11, 17, 3147