In week 3, the Lions hosted the Atlanta Falcons. The Falcons took an early lead in the first quarter with a four-yard touchdown pass from Matt Ryan to Mohamed Sanu. The Falcons scored 13 points in the second quarter via a 36-yard field goal from Matt Bryant, a one-yard touchdown run from Devonta Freeman, and a 48-yard field goal from Bryant. The Lions also scored 13 points in the second quarter via a 55-yard field goal from Matt Prater, a 40-yard field goal from Prater, and a 37-yard interception return from Glover Quin, to make the score 20-13 in favor of Atlanta at half-time. The Falcons extended their lead in the third quarter via a 40-yard field goal from Bryant. The Lions responded with an 11-yard touchdown pass from Matthew Stafford to Golden Tate, and a 35-yard field goal from Prater to tie the game at 23. The Falcons regained the lead in the fourth quarter via a 40-yard touchdown pass from Ryan to Taylor Gabriel. The Lions reduced the Falcons lead to four points with a 57-yard field goal from Prater. The Lions' attempted comeback failed when a touchdown pass from Stafford to Tate was overturned with eight seconds remaining in the game. Due to Tate being ruled down in the field of play and the Lions having no timeouts left, the ten-second runoff rule was invoked, ending the game and giving the Lions their first loss of the season.
Question: How many points did the falcons have at halftime?
Answer: 20