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: ['c', 'P', '139', 'u', 'X', 'H', '2951', 't', 'v', 'L', 'F', 'D', '3241', 'n', '5297', 'Y', '5413']

3, 16, 139, 21, 24, 8, 2951, 20, 22, 12, 6, 4, 3241, 14, 5297, 25, 5413