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', '8091', '4309', '9883', '1261', '1731', 'f', '5201', '7581', '9443', 'r', 'u', 'B']

21, 8091, 4309, 9883, 1261, 1731, 6, 5201, 7581, 9443, 18, 21, 2