Snapping three days of gains, the Sensex at the Bombay Stock Exchange ended with a slim loss of 21 points, or 0.1 percent, at 19,895, today. The Sensex had gained over 530 points in the previous three trading sessions. The Nifty at the National Stock Exchange fell just 1 point, to 5,906.Stock markets in Japan, Hong Kong, South Korea and Singapore declined between 0.1 percent and 1.2 percent.