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', '1807', 'n', 'E', 'x', 's', '5235', 'n', '9899', '7275', 'K', 'o', 'U', '9009', '1533', '8763', '555', 'B', 'g', 'l']

16, 1807, 14, 5, 24, 19, 5235, 14, 9899, 7275, 11, 15, 21, 9009, 1533, 8763, 555, 2, 7, 12