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: ['U', '1115', 'P', 'Z', '4495', 'c', 'u', 'k', 'f', '2671', '415', 'b', 'b', '9351', 'b', 'j', '7971']

21, 1115, 16, 26, 4495, 3, 21, 11, 6, 2671, 415, 2, 2, 9351, 2, 10, 7971