Hoping to rebound from their embarrassing road loss to the Giants, the Seahawks returned home for a Week 6 duel with the Green Bay Packers, as head coach Mike Holmgren faced his former team for the last time.  Also, QB Seneca Wallace was unable to play due to a knee injury he suffered from last week.  QB Charlie Frye was given the start. In the first quarter, Seattle trailed early as Packers kicker Mason Crosby got a 29-yard field goal.  In the second quarter, the Seahawks took the lead as kicker Olindo Mare got a 50-yard field goal, while Frye completed a 6-yard TD pass to rookie TE John Carlson.  Green Bay tied the game as QB Aaron Rodgers got a 1-yard TD run. In the third quarter, the Packers regained the lead as Rodgers completed a 45-yard TD pass to WR Greg Jennings.  In the fourth quarter, Green Bay pulled away as Rodgers completed a 1-yard TD pass to FB John Kuhn, along with Crosby nailing a 51-yard field goal.  Seattle tried to come back as Frye completed a 5-yard TD pass to WR Keary Colbert, but the Packers' defense was too much.
Question: How many yards longer was Mare's first half field goal compared to Crosby's first half field goal?
Answer: 21