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: ['1297', 'H', '8761', 'b', 'g', 'b', '6053', '3641', '3507', '1457', 'U', '8725', 'a', '457', '6555', 'R', 'l', 'g', '9543', '4403']

1297, 8, 8761, 2, 7, 2, 6053, 3641, 3507, 1457, 21, 8725, 1, 457, 6555, 18, 12, 7, 9543, 4403