You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

what is the first event mentioned?, Context: The Russian Revolution is the series of revolutions in Russia in 1917, which destroyed the Tsarist autocracy and led to the creation of the Soviet Union. Following the abdication of Nicholas II of Russia, the Russian Provisional Government was established. In October 1917, a red faction revolution occurred in which the Red Guard, armed groups of workers and deserting soldiers directed by the Bolshevik Party, seized control of Saint Petersburg (then known as Petrograd) and began an immediate armed takeover of cities and villages throughout the former Russian Empire.
Solution: Russian Revolution
Why? This is a good example, and the Russian Revolution is the first event mentioned.

New input: Which happened first, 484 was added to the 610 area or Southeastern Pennsylvania was assigned the 215 area code?, Context: Southeastern Pennsylvania was assigned the 215 area code in 1947 when the North American Numbering Plan of the "Bell System" went into effect. The geographic area covered by the code was split nearly in half in 1994 when area code 610 was created, with the city and its northern suburbs retaining 215. Overlay area code 267 was added to the 215 service area in 1997, and 484 was added to the 610 area in 1999. A plan in 2001 to introduce a third overlay code to both service areas (area code 445 to 215, area code 835 to 610) was delayed and later rescinded.
Solution:
Southeastern Pennsylvania was assigned the 215 area code