After a tough road loss to the Ravens, the Steelers went home for a game against the Dolphins.  They would score first as Ben Roethlisberger found Emmanuel Sanders on a 5-yard pass for a 7-0 lead.  The Dolphins managed to get on the board as Caleb Sturgis kicked a 30-yard field goal making the score 7-3.  In the 2nd quarter, Charles Clay caught a 6-yard touchdown pass from Ryan Tannehill as the Phins took the lead 10-7 at halftime.  After the break, the Dolphins went right back to work as Daniel Thomas ran for a 4-yard touchdown making the score 17-7.  The Steelers then came within 3 when Roethlisberger found Antonio Brown on a 43-yard touchdown pass making the score 17-14 and would eventually score again when Troy Polamalu picked off Tannehill and returned it 19 yards for a touchdown as they retook the lead 21-17.  The Dolphins however moved back into the lead as Tannehill found Brian Hartline on a 4-yard pass for a 24-21 score.  In the 4th quarter, Roethlisberger found Jerricho Cotchery on a 16-yard touchdown pass as they moved ahead 28-24.  Clay then caught a pass from Tannehill making the score 31-28 as the Dolphins retook the lead.  They would stop scoring after Sturgis kicked a 27-yard field goal for a 34-28 lead.  Under a minute to go in the quarter, the Steelers got the ball back with Roethlisberger throwing to Brown and then Brown running for what seemed to be the game-tying (and eventually game-winning touchdown and PAT), but officials reviewed the play and it was determined that Brown had stepped out of bounds during the run ending the game dropping the team to 5-8.
Question: How many yards was the longest rushing touchdown?
Answer: 4