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: ['3543', '1509', '903', 'C', '5641', 'U', 'S', 'R', '3699', '9305', 'o', '4983', '1893', 'c', '6721', 'F', '1965', '7947', '9311', 'o', '6213', '4467', '1839', '203', 'B', '1123', 'Q', 'H', '7103', '9521']

3543, 1509, 903, 3, 5641, 21, 19, 18, 3699, 9305, 15, 4983, 1893, 3, 6721, 6, 1965, 7947, 9311, 15, 6213, 4467, 1839, 203, 2, 1123, 17, 8, 7103, 9521