Definition: Classify the relation of question with context to one of these categories: 1) award received, 2) based on, collection, 3) conflict, 4) constellation, 5) convicted of, 6) date of death, 7) director, 8) drafted by, 9) educated at, 10) medical condition, 11) military branch, 12) narrative location, 13) occupation, 14) original network, 15) parent company, 16) point in time, 17) production company, 18) residence, 19) series, 20) service entry, 21) sex or gender, 22) spouse, 23) standards body question.

Positive Example 1 -
Input: Context : Isaac Nicola Romero (1916 in Havana, Cuba -- 1997) was a prominent Cuban guitarist and one of the founders of the modern Cuban Guitar School. 
Question : What was Isaac Nicola's city of birth?
Output: place of birth

Positive Example 2 -
Input: Context : Both Timur and Demir are popular male names in Turkey today. 
Question : What was the title that Timur held?
Output: noble title

Negative Example 1 -
Input: Context : Faye Wong (born 8 August 1969) is a Chinese singer-songwriter and actress based in Hong Kong, often referred to as a ``diva'' in Hong Kong media. 
Question : When did Faye Wong born ?
Output: sex or gender

Negative Example 2 -
Input: Context : The Boeing 601 (sometimes referred to as the BSS-601, and previously as the HS-601) is a communications satellite bus introduced in 1987 by Hughes Space and Communications Company. 
Question : Which was the official year for the approval of Boeing 601?
Output: time of invension

Now complete the following example -
Input: Context : The Buk missile system (Russian: ``Бук''; ``beech'' (tree), /bʊk/) is a family of self-propelled, medium-range surface-to-air missile systems developed by the Soviet Union and its successor state, the Russian Federation, and designed to fight cruise missiles, smart bombs, fixed- and rotary-wing aircraft, and unmanned aerial vehicles. 
Question : What was the year that Buk missile system entered service?
Output: 


Answer: service entry