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: ['O', '781', '7615', 'Q', 'O', 'f', 'S', '6849', 'E', 'X', 'z', '4931', 'u', '6663', 'A', '9185', '8799']

15, 781, 7615, 17, 15, 6, 19, 6849, 5, 24, 26, 4931, 21, 6663, 1, 9185, 8799