The Chiefs took an early lead on a 30-yard pass from Tyler Thigpen to Mark Bradley.  The Chiefs defense continued to show improvement in the red zone, limiting the Chargers to two field goals instead of two touch downs.  At the end of the first half, Thigpen threw a pass to 34&#160;yard touchdown pass to Tony Gonzalez. However, the extra point snap was botched and an attempt at a quick pass failed. The Chargers controlled the second half better than the first, scoring two touchdowns and leading the Chiefs by 7 at the end of the fourth quarter.  The Chiefs' final drive ended with a 3-yard touchdown pass to Gonzalez. A 1-point PAT would tie the game. However, Herm Edwards told Thigpen to go for two, explaining in a post-game interview that the defense was too beat up for overtime play.  The resulting two-point conversion ended in an incomplete pass.  The Chiefs lost by one point.
Answer this question: How many points did the Chiefs score in the first half?
13