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: ['o', 'l', 'R', 'F', '7967', 'K', '8783', '6393', 'b', 'U', '9909', 'r']

15, 12, 18, 6, 7967, 11, 8783, 6393, 2, 21, 9909, 18