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: ['1481', '6749', '3939', 'r', 'c', '731', 't', 'b', 'C', '3651', 'A', '7563', '6911', '2161', 'G', 'A', 'S', 't', '2897', 'S', '1389', '7413', '7087', 'd', 'R', '5139', 'd', 'C', 'M', '9251', 'O']

1481, 6749, 3939, 18, 3, 731, 20, 2, 3, 3651, 1, 7563, 6911, 2161, 7, 1, 19, 20, 2897, 19, 1389, 7413, 7087, 4, 18, 5139, 4, 3, 13, 9251, 15