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', 'l', 'O', '2863', 'F', '623', '151', '5087', '6439', 'Q']

19, 12, 15, 2863, 6, 623, 151, 5087, 6439, 17