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: ['21', '8993', 'o', '2517', 'i', 'R', 'X', 'm', 'f', 'v', 'Z', 's', '2493', '1967', 'S', 'L', 'd', 'Y', '4755', 'S']

21, 8993, 15, 2517, 9, 18, 24, 13, 6, 22, 26, 19, 2493, 1967, 19, 12, 4, 25, 4755, 19