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: ['L', '543', '4223', 'u', '8951', '3433', 'C', 'J', '8321', '2929', '3989', 'e', '2791', 'a', '1571', 'a']

12, 543, 4223, 21, 8951, 3433, 3, 10, 8321, 2929, 3989, 5, 2791, 1, 1571, 1