Task: Question Answering
Input (English): Passage: The 49ers would score touchdowns on each of three Cowboys turnovers, all before halftime. Even though the Cowboys held a significant edge in 1st quarter time of possession (13:26 to 1:34), the 49ers had a 21-3 lead due to the turnovers. With the 49ers up 28-3, the Cowboys would find themselves with their largest halftime deficit in a home opener ever. Although the 49ers would not score again in the second half, they would only hold the Cowboys to 14 more points, and win the game. 
Question: how many points did the niners lead by? 
Answer type: Number 
Output (English): 21.