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: ['P', 't', 'o', '1821', 'z', '5287', '587', 'f', '2369', '8435', '3767', 'N', '5735', '7329', 'Z', '5963', '8839', '881', 'U', 'p', '7861', '6129']

16, 20, 15, 1821, 26, 5287, 587, 6, 2369, 8435, 3767, 14, 5735, 7329, 26, 5963, 8839, 881, 21, 16, 7861, 6129