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: ['s', '6787', 'l', '4257', 'B', 'S', 'e', '9841', '8737', 'U', '2719', 'F', '8045', '8769', 'E', 'M', '983', '5929', '8827']

19, 6787, 12, 4257, 2, 19, 5, 9841, 8737, 21, 2719, 6, 8045, 8769, 5, 13, 983, 5929, 8827