Answer based on context:

Due to a conflict involving the Orioles' schedule, the Ravens opened the regular season on the road against the Broncos in what would be the first time a defending Super Bowl champion team has done so since the Buccaneers in 2003 when they opened their regular season against the Eagles.  This would be a rematch of last year's AFC Divisional game. The Ravens drew first blood when Joe Flacco found Vonta Leach on a 2-yard touchdown pass to take the lead 7-0 in the first quarter for the only score of the period.  The Broncos would tie the game in the 2nd quarter with Peyton Manning finding Julius Thomas on a 24-yard pass to take the game to 7-7.  The Ravens moved back into the lead when Ray Rice ran for a 1-yard touchdown to make the score 14-7.  Peyton would find Julius again on a 23-yard pass to make the score 14-14 for another tie before the Ravens kicker Justin Tucker nailed a 25-yard field goal to make the score 17-14 at halftime.  In the 3rd quarter, the Broncos went right back to work as Peyton found Andre Caldwell on a 28-yard touchdown pass to take a 21-17 lead followed up with finding Wes Welker on 2 consecutive passes from 5 yards and 2 yards out for an increase in the lead first to 28-17 and then to 35-17.  Later on in the quarter, Peyton would find Demaryius Thomas on a 26-yard pass to increase the lead to 42-17.  The Ravens tried to rally a comeback in the last quarter, with Flacco finding Marlon Brown on a 13-yard pass to shorten the Broncos' lead 42-24 followed up by Tucker's 30-yard field goal to make the score 42-27.  However, the Broncos wrapped things up in the game when Peyton found D. Thomas again on a 78-yard pass to make the final score 49-27.  The Ravens began their season 0-1 for the first time under John Harbaugh as head coach and Joe Flacco as their starter.  They also lost their first regular season opening game since 2007 as well as becoming the 2nd straight defending Super Bowl champion team to lose their season opener.

How many points did Baltimore lead by at halftime?
3