def sam_list(sam):
    """
	get a list of mapped reads
	"""
    list = []
    for file in sam:
        for line in file:
            if line.startswith('@') is False:
                line = line.strip().split()
                id, map = line[0], int(line[1])
                if map != 4 and map != 8:
                    list.append(id)
    return set(list)
