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: ['f', 'M', '4323', '1261', 'O', '5479', 'D', '3187', 'm', 'U', 'c', '6735', '3693', '6611', '1629']

6, 13, 4323, 1261, 15, 5479, 4, 3187, 13, 21, 3, 6735, 3693, 6611, 1629