In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

Example Input: What was Cork City formerly surrounded by?, Context: The city's charter was granted by Prince John, as Lord of Ireland, in 1185. The city was once fully walled, and some wall sections and gates remain today. For much of the Middle Ages, Cork city was an outpost of Old English culture in the midst of a predominantly hostile Gaelic countryside and cut off from the English government in the Pale around Dublin. Neighbouring Gaelic and Hiberno-Norman lords extorted "Black Rent" from the citizens to keep them from attacking the city. The present extent of the city has exceeded the medieval boundaries of the Barony of Cork City; it now takes in much of the neighbouring Barony of Cork. Together, these baronies are located between the Barony of Barrymore to the east, Muskerry East to the west and Kerrycurrihy to the south.
Example Output: wall

Example Input: What is a legal doctrine that obligates courts to follow historical cases when making a ruling on a similar case, Context: Federal law originates with the Constitution, which gives Congress the power to enact statutes for certain limited purposes like regulating interstate commerce. The United States Code is the official compilation and codification of the general and permanent federal statutes. Many statutes give executive branch agencies the power to create regulations, which are published in the Federal Register and codified into the Code of Federal Regulations. Regulations generally also carry the force of law under the Chevron doctrine. Many lawsuits turn on the meaning of a federal statute or regulation, and judicial interpretations of such meaning carry legal force under the principle of stare decisis.
Example Output: stare decisis

Example Input: What is the number 1 single agent killer, Context: The top three single agent/disease killers are HIV/AIDS, TB and malaria. While the number of deaths due to nearly every disease have decreased, deaths due to HIV/AIDS have increased fourfold. Childhood diseases include pertussis, poliomyelitis, diphtheria, measles and tetanus. Children also make up a large percentage of lower respiratory and diarrheal deaths. In 2012, approximately 3.1 million people have died due to lower respiratory infections, making it the number 4 leading cause of death in the world.
Example Output:
HIV/AIDS