The Bengals started their season on the road against the Raiders. They would score first when Jeremy Hill ran for a TD from 3 yards out 7-0 lead in the first quarter for that quarter's only score.  They increase their lead in the second quarter when Mike Nugent nailed a 32-yard field goal for a 10-0 lead followed up by Hill running for a 2-yard TD for a 17-0 lead followed up by Andy Dalton finding Tyler Eifert on a 13-yard TD pass for a 24-0 lead at halftime.  After the break, the Bengals went back to work as Dalton and Eifert hooked up again this time on an 8-yard TD pass (with a failed PAT) for a 30-0 lead.  Nugent put a 35-yard field goal through for a 33-0 lead.  In the fourth quarter, it was all Raiders when Backup QB Matt McGloin found Marcel Reese on 2 straight TD passes:  from 11 and 9 yards out (with a failed 2-point conversion) for 33-7 and the final score of 33-13. With the win, the Bengals started their season 1-0.  The team would also improve to 1-10 against the Raiders in Oakland.
Question: How many yards was the longest touchdown of the first half?
Answer: 13