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', '1913', 'J', 'x', '5059', '1277', '6161', 'C', '1083', '9465', 'Z', '781', '5019', 'Y', 'M', 'l', 'O', 'T', '9999', 'N', '2975', '59', 'w', '2999', 't', 'D', 'U', '5747', '3865', '1397']

21, 1913, 10, 24, 5059, 1277, 6161, 3, 1083, 9465, 26, 781, 5019, 25, 13, 12, 15, 20, 9999, 14, 2975, 59, 23, 2999, 20, 4, 21, 5747, 3865, 1397