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: ['21', 'a', 'f', '8479', 'n', 'f', 's', '4191', 'h', 'C', 'o', '4397', '9879', 'T', '9823', '7989', 'i', 'c', 'P']

21, 1, 6, 8479, 14, 6, 19, 4191, 8, 3, 15, 4397, 9879, 20, 9823, 7989, 9, 3, 16