#change 2019/05/21:
#change 2019/05/14:
#change 2019/04/03
#change 2019/01/04
#change 2018/11/01
#change 2018/08/21
Dark chain detection
#change 2019/05/21:
#change 2019/05/14:
#change 2019/04/03
#change 2019/01/04
#change 2018/11/01
#change 2018/08/21
Dark chain detection