After resting up from their bye week, the Raiders went back to the O.co Coliseum for a home game against the Chargers.  In the first quarter, they snagged an early 7-0 lead when Derek Carr found Andre Holmes on a 77-yard touchdown pass.  Later on, the Chargers would tie it up 7-7 when Philip Rivers found Eddie Royal on a 29-yard touchdown pass.  In the 2nd quarter, the Chargers took the lead when Rivers found Malcom Floyd on a 5-yard touchdown pass for a 14-7 game.  However, the Raiders managed to tie it up before halftime when Carr found James Jones on a 6-yard touchdown pass for a 14-14 game.  In the 3rd quarter, the Raiders retook the lead when Carr found Brice Butler on a 47-yard touchdown pass leading 21-14.  The Chargers however tied it back up when Rivers found Antonio Gates on a 1-yard touchdown pass for a 21-21 game.  In the 4th quarter, the Raiders retook the lead again when Carr found Holmes again on a 6-yard touchdown pass for a 28-21 game.  However, the Chargers were able to score 10 points later on in the quarter:  First when Nick Novak scored a field goal from 30 yards out to come within 4, 28-24 and then Branden Oliver's 1-yard run for a touchdown for the eventual final score of 31-28.
How many touchdowns were scored in the first half?
4