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: ['7215', 'G', '9919', '1137', 't', '3137', 'B', 'P', '5861', 'S', '9719', 'U', '2813', 'X', 'g', 'N', '5609', '1633', '6473', '4477', 'k', 't', 'P', 'g', 'y', 'B', '5871', '2891', '3767', '3875', '1969', '9275', 'M', '9663', '321', 'O']

7215, 7, 9919, 1137, 20, 3137, 2, 16, 5861, 19, 9719, 21, 2813, 24, 7, 14, 5609, 1633, 6473, 4477, 11, 20, 16, 7, 25, 2, 5871, 2891, 3767, 3875, 1969, 9275, 13, 9663, 321, 15