Snapping a four-day rally, the Sensex at the Bombay Stock Exchange ended with a marginal loss of 3 points, at 18,486, today, on profit-booking by investors. The Sensex had rallied more than 865 points in the past four trading sessions. But the Nifty at the National Stock Exchange managed to gain 3 points, to 5,539.In other regional markets, the key indices in Japan, China, Hong Kong, South Korea and Singapore gained between 0.8 percent and 1.7 percent.