def ith_byte_block(block_size: int, i: int) -> int:
    """
    Return the block to which the byte at index i belongs.
    :param block_size: The block size.
    :param i: The index of the interesting byte.
    :return: The index of the block to which the byte at index i belongs.
    """
    assert block_size > 0
    assert i >= 0
    return i // block_size