4399
Varian Medical Systems  of  Palo Alto  California made its first linear accelerator optimized for stereotactic radiosurgery in 1992 called the Clinac 600SR .
 city of headquarters: Varian Medical Systems, Palo Alto
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: Varian Medical Systems, Palo Alto