Continuing its relentless slide for the fifth straight session, the Sensex at the Bombay Stock Exchange plunged 306 points, or 1.7 percent, to a 5-month low of 18,022, on Tuesday. During the session, the Sensex had slipped below the psychological 18,000 mark. The market fell on fears of inflation, and rising input costs and interest rates crimping corporate profits. The Sensex has already lost 825 points in the previous four trading sessions. The Nifty at the National Stock Exchange declined 89 points, or 1.6 percent, to 5,417.But stock markets in Japan, China, Hong Kong, South Korea and Singapore rose between 0.1 percent and 0.4 percent.