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', 'x', 'o', 'S', 'A', '621', '1715']

25, 24, 15, 19, 1, 621, 1715