def pretty_size(size):
    if size >= 1024*1024*1024:
        return "%.1f GiB" % round(size/1024/1024/1024.0)
    elif size >= 1024*1024:
        return "%.1f MiB" % round(size/1024/1024.0)
    elif size >= 1024:
        return "%.1f KiB" % round(size/1024.0)
    else:
        return "%u B" % size