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: ['1273', '9449', 'o', 'k', 'X', 'N', 'i', '2875', '5403', '549', 'a', '4211', '5583', '5739', 'S', 'U', 'N', 'f']

1273, 9449, 15, 11, 24, 14, 9, 2875, 5403, 549, 1, 4211, 5583, 5739, 19, 21, 14, 6