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: ['r', '853', '139', '2425', 'b', '4003', '7571', '9029', '9437', 'I', 'P', '2917', '2687']

18, 853, 139, 2425, 2, 4003, 7571, 9029, 9437, 9, 16, 2917, 2687