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: ['y', '7053', '5843', '2151', 'a', '6315', '5981', 'E', 'W', 'S', 'y', '9999']

25, 7053, 5843, 2151, 1, 6315, 5981, 5, 23, 19, 25, 9999