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: What caused the system to freeze?, Context: The original model Famicom featured two game controllers, both of which were hardwired to the back of the console. The second controller lacked the START and SELECT buttons, but featured a small microphone. Relatively few games made use of this feature. The earliest produced Famicom units initially had square A and B buttons. This was changed to the circular designs because of the square buttons being caught in the controller casing when pressed down and glitches within the hardware causing the system to freeze occasionally while playing a game.
Solution:
square buttons being caught in the controller casing