A boat sails from the pier at Fisherman's Wharf in San Francisco at 1 m/s, directly toward Alcatraz Island. A kite rider heads directly away from Alcatraz toward the boat at 3 m/s, according to the skipper of the sailboat. Calculate the velocity of the kite rider relative to the pier. (Assume the origin is at the pier, and the +x axis points towards Alcatraz Island. Indicate the direction with the sign of your answer.)