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: ['9915', 'u', 'A', 'R', '9957', '7001', 'f', '191', '6695', '7051', '6539', 'a', '8493', 'o', 'f', '2233', 'U', 'C', 'l', '8721', '6559', 'H', '7963', '3567', '5223', '2397', 'C', 't', 'q', '5987', '1883', 'r', 'M', '6815', 'm', '6481', '8003']

9915, 21, 1, 18, 9957, 7001, 6, 191, 6695, 7051, 6539, 1, 8493, 15, 6, 2233, 21, 3, 12, 8721, 6559, 8, 7963, 3567, 5223, 2397, 3, 20, 17, 5987, 1883, 18, 13, 6815, 13, 6481, 8003