Buddhist monks walk at a temple in Koyasan in Koya, Wakayama prefecture, June 25, 2013. The 1,200-year-old Koyasan, a World Heritage site deep in the mountains of western Japan and long prized as a haven for quiet contemplation. But in recent months monks here have been debating a very worldly question: How did a complex bet on the yen go so horribly wrong? Picture taken June 25, 2013. To match Feature JAPAN/DERIVATIVES REUTERS/Hideyuki Sano (JAPAN - Tags: BUSINESS POLITICS)