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: ['p', '7615', 'C', '5639', 'A', '917', '4145', 'F', 'D', 'X', 'S', '7827', '3819', '7113', 'l', '8829', 'F', '8025', '3609', '3757', 'u']

16, 7615, 3, 5639, 1, 917, 4145, 6, 4, 24, 19, 7827, 3819, 7113, 12, 8829, 6, 8025, 3609, 3757, 21