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: ['L', '1865', 'U', '719', 'H', '9871', 'm', 'L', 'J', 't', 'p', 'A', '3929', 'B']

12, 1865, 21, 719, 8, 9871, 13, 12, 10, 20, 16, 1, 3929, 2