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: ['6881', 'F', '4759', '5797', '4879', '5761', '9913', '8509', 'c', 'X', 'U']

6881, 6, 4759, 5797, 4879, 5761, 9913, 8509, 3, 24, 21