Abstract: The last k days of trading together tell the financial market trends. It may be inconceivable if we are told to ignore the 3rd, 6th, and 8th day, a priori. We introduce a novel approach to show exactly that — it pays to ignore some fixed days among the recent k days, fixed a priori, in order to minimize risk and maximize profit simultaneously. The theory developed here has direct implications to our common senses on how we should look at the financial market trends. Key Words: optimal spaced seeds, market trend prediction Category: F.0, J.0