Elementary school students scream at a mud flat as they participate in a summer military camp for civilians at the Cheongryong Self-denial Training Camp run by retired marines in Ansan, about 40 km (25 miles) southwest of Seoul, July 21, 2011. [Photo/Agencies]

Elementary school students take a nap on a floor after a morning exercise as they participate in a summer military camp for civilians at the Cheongryong Self-denial Training Camp run by retired marines in Ansan, about 40 km (25 miles) southwest of Seoul, July 21, 2011. [Photo/Agencies]