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', '2053', '4703', '8359', 'U', 'r', '1947', '4205', '6819', '9843', '4383', 'w', 'V', '711', '5089', '1539', '651', 'r', '3135', '1797']

21, 2053, 4703, 8359, 21, 18, 1947, 4205, 6819, 9843, 4383, 23, 22, 711, 5089, 1539, 651, 18, 3135, 1797