def store_clip_pos(locus, chr, seq, flag, CLIP_note):
    """
	A data structure store info of soft-clippings.
	It has two hashtables:
		1. key1 is an integer calculated by coordinate / 10000;
		2. key2 is an integer calculated by (coordinate % 10000) / 50.
	"""
    hash_1 = int(locus / 10000)
    mod = locus % 10000
    hash_2 = int(mod / 50)
    element = [locus, seq, flag]
    if hash_1 not in CLIP_note[chr]:
        CLIP_note[chr][hash_1] = dict()
        CLIP_note[chr][hash_1][hash_2] = list()
        CLIP_note[chr][hash_1][hash_2].append(element)
    elif hash_2 not in CLIP_note[chr][hash_1]:
        CLIP_note[chr][hash_1][hash_2] = list()
        CLIP_note[chr][hash_1][hash_2].append(element)
    else:
        CLIP_note[chr][hash_1][hash_2].append(element)
