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: ['749', 'Y', 'U', '1801', 'k', 'j', 'a', 'U', '1545', 'i', '229', 'D', 'R']

749, 25, 21, 1801, 11, 10, 1, 21, 1545, 9, 229, 4, 18