Given the task definition and input, reply with output. 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.

['Y', '393', '2369', '3131', '5595', '7807', '5545', '2503', 'U', 'd', 'n', 'I', '6793', '4681', '9959', '6397', '2057', '6697', 't']
25, 393, 2369, 3131, 5595, 7807, 5545, 2503, 21, 4, 14, 9, 6793, 4681, 9959, 6397, 2057, 6697, 20