def get_column_alphabetical_index_from_zero_indexed_num(col_idx: int) -> str:
    """Convert zero-index column number to alphabetical base-26 (e.g. 0 -> 'A', 27 -> 'AA'"""
    num_letters_alphabet = 26

    def get_letter_from_zero_indexed_idx(idx: int):
        ascii_start = 65
        return chr(ascii_start + idx)

    prefix_str = ''
    if col_idx < num_letters_alphabet:
        return get_letter_from_zero_indexed_idx(col_idx)
    last_char = get_letter_from_zero_indexed_idx(col_idx % num_letters_alphabet)
    prefix_str = get_column_alphabetical_index_from_zero_indexed_num(col_idx // num_letters_alphabet)
    return prefix_str + last_char