A doorman's hat at Sheraton hotel, a brand of Starwood Hotels & Resorts Worldwide, is pictured in Warsaw February 24, 2012. REUTERS/Kacper Pempel

A doorman’s hat at Sheraton hotel, a brand of Starwood Hotels & Resorts Worldwide, is pictured in Warsaw February 24, 2012. REUTERS/Kacper Pempel

A doorman's hat at Sheraton hotel, a brand of Starwood Hotels & Resorts Worldwide, is pictured in Warsaw February 24, 2012. REUTERS/Kacper Pempel

March 14, 2016 11:48 AM (UTC+8)