4017
Attendees at the  Istanbul  meeting included representatives of the 1920  Revolution Brigades  and the al-Rashideen Army which were among the Sunni insurgent groups formed to fight the U.S. occupation .
 city of headquarters: Istanbul, Revolution Brigades
Given a phrase that describes the relationship between two words, extract the words and the lexical relationship between them. The output format should be "relation1: word1, word2; relation2: word3, word4". 
Option: cities of residence, top members employees, members, alternate names, origin, state or provinces of residence, title of person, spouse, city of headquarters, NA, founded by, state or province of headquarters, employee of, countries of residence, country of birth, founded, subsidiaries, country of headquarters 
Text: {0} 
Answer:
 city of headquarters: Istanbul, Revolution Brigades