Volunteers walk on the street in Qingdao, East China's Shandong province, June 1, 2018. The 18th Shanghai Cooperation Organization (SCO) Summit is scheduled for June 9-10 in Qingdao. Volunteers are easily seen on the street. [Photo/Xinhua]

Volunteers give information to tourists at a service station in Qingdao, East China's Shandong province, June 2, 2018. [Photo/Xinhua]

Photo shows the supplies stored at a volunteer service station at the May Fourth Square in Qingdao, East China's Shandong province, June 3, 2018. [Photo/Xinhua]