adcelannotate = {"mobilepaywallcategory" : "MOBILE_PREM-BUSINESS","nativepaywallcategory" : "NATIVE_PREM-BUSINESS"};Greece's top companies lost billions in market value in a matter of minutes on Monday, when the stock exchange plunged upon reopening after a five-week closure and investors worried over a dramatic new drop in the economy. The main stock index shed over 22 percent soon after the open, as traders got their first opportunity since late June to react to the latest twists in the country's economic drama.