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: ['7431', 'o', '2619', '7545', 'C', 'c', 'i', '8445', 'l', '1539', 'p', 'u', 'M', '1291']

7431, 15, 2619, 7545, 3, 3, 9, 8445, 12, 1539, 16, 21, 13, 1291