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: ['U', '999', 'i', '6995', '8953', 'e', 'v', '1223', 'B', 't', '5611', '7473', 'b', 'S', 'p', '2041', '4317', '909', 'y', 'W', 'x', 'q', 'T', 'P', 'b', 'j', 'd', '2899', '6475', '149', '2687', '5219', 'K', 'm', 'P', 'A']

21, 999, 9, 6995, 8953, 5, 22, 1223, 2, 20, 5611, 7473, 2, 19, 16, 2041, 4317, 909, 25, 23, 24, 17, 20, 16, 2, 10, 4, 2899, 6475, 149, 2687, 5219, 11, 13, 16, 1