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: ['6873', 'L', 'E', 'F', 'B', 'K', 'a', 'k', 'V', '8707', 'u', '2909', 'L', 'Q', 'E', '575', 'y', 'D', '9555', 'H', '519', 'a', '8009', '7977', '1933', '7775', '2365', 'R', '9007', '9199', 'n', 'r', 'X', '8857', '5377', '5455', 'u', 'm', 'H', '3457']

6873, 12, 5, 6, 2, 11, 1, 11, 22, 8707, 21, 2909, 12, 17, 5, 575, 25, 4, 9555, 8, 519, 1, 8009, 7977, 1933, 7775, 2365, 18, 9007, 9199, 14, 18, 24, 8857, 5377, 5455, 21, 13, 8, 3457