def to_letters(number_message: list) -> str:
    """
    Converts list of numbers into uppercase string.
    Numbers in list should be in range [11, 36] for proper ASCII decoding.
    [11, 36] + 54 = [65, 90], i.e. A-Z
    """
    return "".join([chr(number + 54) for number in number_message])