In week 6, the Lions hosted the NFC West Division-leading San Francisco 49ers. The Lions struck first, when Jason Hanson kicked a 25-yard field goal that came after a San Francisco turnover. Detroit added to their lead when Brandon Pettigrew caught a 16-yard TD pass. In the second quarter, the 49ers finally got on the board with a 1-yard TD run by Frank Gore. San Francisco received a safety when Aldon Smith sacked Matthew Stafford in the end zone. The final points of the first half came just before intermission when David Akers of the 49ers kicked a 55-yard field goal, putting the Lions down at halftime for the fourth consecutive week. After the break, Detroit scored on a 24-yard field goal. San Francisco responded with a field goal of their own, this one from 31 yards out. In the fourth quarter, the Lions' Nate Burleson caught a 5-yard TD pass; the Lions went for a 2-point conversion but Calvin Johnson failed to catch Matthew Stafford's pass. In the final 2 minutes, the 49ers rallied from behind, first with a 6-yard TD catch by Delanie Walker, then a 37-yard field goal by David Akers, putting them up 25-19. With 1:02 left in the game, the Lions attempted another comeback, but San Francisco's defense held them off, handing Detroit its first loss of the season as the team fell to 5-1 and 2nd place in the NFC North. After the game, coaches Jim Schwartz and Jim Harbaugh got into an argument after Schwartz claimed Harbaugh pushed him out of the way when the two coaches were shaking hands.
Question: how many yards did san Francisco get?
Answer: 31