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: ['G', 'a', '6247', '2413', 'H', '9915', '897', '7855', '1243', '1923', '3815', '5343', 'x', 'c', '5517', '9487', 'b', '273', '4905', 'W', 'G', 'B', 'u']

7, 1, 6247, 2413, 8, 9915, 897, 7855, 1243, 1923, 3815, 5343, 24, 3, 5517, 9487, 2, 273, 4905, 23, 7, 2, 21