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: ['3559', '8555', '6765', 'A', 'F', '1597', '6321', '2681', 'o', 'u', '1627', 'Z', '9881', '1467', 'R']

3559, 8555, 6765, 1, 6, 1597, 6321, 2681, 15, 21, 1627, 26, 9881, 1467, 18