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: ['S', '6599', 'i', 'u', '7321', '859', '171', '7539', 'u', 'q', 'Y', '5699', '5409', 'C', '2885', '8065', '4941', '5981']

19, 6599, 9, 21, 7321, 859, 171, 7539, 21, 17, 25, 5699, 5409, 3, 2885, 8065, 4941, 5981